Regina King had a hard time convincing some of her friends about Watchmen, her new HBO series inspired by the DC comic book of the same name and featuring the kind of details that make some people run for the exits: time travel, kung-fu fighting, masks and thinly veiled political allegory. “Girl, don’t do this,” said one friend. King could only smile and agree.

But we would all do well to watch King – in anything. At 48, she is in her prime. While filming Watchmen, King won the best supporting actress Oscar for If Beale Street Could Talk, based on the James Baldwin novel. For years, she has been turning out quietly devastating portraits – in the movies Jerry Maguire and Ray, in the TV show Southland – with little public recognition. Now she has her pick of roles. “I appreciate winning the Oscar,” she says, “but that’s not the ultimate goal. I should be able to use it as currency moving forward.”

King was not familiar with the original Watchmen material, nor the 2009 Zack Snyder movie (her 23-year-old son Ian is more excited about this role than any of King’s previous parts). But once she read the script, she was enthused. In Damon Lindelof’s adaptation, the tale’s 1950s cold-war storyline is spun into a look at the rise of a white supremacist group in a parallel US. King plays Angela Abar, a cop with superhuman fighting skills and an amazing French Lieutenant’s Woman-style cape: not the kind of part she usually gets.

Facebook Twitter Pinterest Veiled threat … King as the superhero in Watchmen. Photograph: AP

King, who in a New York hotel room is slight and smiling, powers through the series like a wrecking ball. She tuned into the fantasy landscape pretty quickly, even quibbling with wardrobe over the practicality of each costume. Originally, her mask was so cumbersome it seemed to defy even the tenuous reality of a comic-book tale. “I was like, ‘This is not good for the superhero peripheral! I can’t see if something’s coming – you have to tell me!’ So our wardrobe designer had a great idea: what if it was painted on?” It was hell on her skin, but it’s dynamite on screen.

Lindelof was co-creator of Lost and the recent HBO hit The Leftovers. Watchmen has that same compelling narrative, the story of men with bamboo torches trying to eliminate black people. In the current climate, this parallel America feels very like the real thing. One of Lindelof’s triggers, says King, was Ta-Nehisi Coates’s 2014 article for the Atlantic, The Case for Reparations, addressing the unacknowledged fall-out from slavery. She also cites “the way policing is happening here in the States with, particularly, black men.”

To this end, Watchmen is, oddly, of a piece with Beale Street, Baldwin’s exposé of the split-screen reality in the US between white people and people of colour – although Watchmen doesn’t seem expressly political to King. With a laugh, she says: “Being black, it’s part of my life. What’s happened is that Trump has just emboldened people. They were always there, feeling the way they’ve been feeling, but now, oh my gosh. There are a lot of people – white friends I have – who have had this wedge in their families. They knew maybe a family member was a little less progressive, but whoa! Now they’re finding out their views were so far apart.”

Trump has just emboldened people. They were always there, feeling the way they’ve been feeling, but now, oh my gosh

Meanwhile, the idea of white supremacy as a guerrilla force is not exactly fantastical, given the extent such militias play in US history. “It’s easy to pretend that something didn’t exist if you’re not talking about it,” says King. “Within our community, yes, we’re talking about it all the time, because we’re living it generation to generation. But for a lot of white Americans, ignorance is bliss. For them.”

King grew up in California, and wanted to be a dentist. This was not a passing phase. She loved going to her dentist so much, it seemed for many years to be the only possible career path. “I would always hear horror stories about the dentist, but not mine. His dental assistant was his wife, Babe, and she had this white hair that looked like cotton candy. I always looked forward to going. I’d floss to impress him. He made the experience fun. He made me understand how important your periodontal situation is.” She bursts out laughing. “He had a great set of teeth and Babe had a great set of teeth! So whenever I would see people without a great set of teeth I’d be like, ‘Ew!’”

Don’t ever live in Britain, I say. “Yeah, I know.” Again she hoots with laughter. “Not a lot of good teeth there.”

King had acted in school, but it wasn’t until she got to theUniversity of Southern California that it became clear to her not only that dental work wasn’t in her future, but that what she should do was drop out to act. It amazes her now that she made this decision with “no information to back it up”. She simply knew it was the right thing to do, a strong intuition foreshadowing a steeliness that would become apparent 30 years later in her most famous roles. Her parents weren’t happy. “My mom is a teacher and showed her disappointment,” she says, “but not enough that it made me decide to go back.”

Facebook Twitter Pinterest Quiet marvel … King giving her Oscar-winning turn in If Beale Street Could Talk. Photograph: Annapurna Pictures/Allstar

She was so young and inexperienced that for years, in roles she took in movies such as Boyz N the Hood and Mighty Joe Young, she had no idea of pay scale, or whether she was receiving a fair income relative to others on set. “I wasn’t focused on that,” she says. “It wasn’t until I was in my 30s that I even stopped to consider the wage gap. It was something as simple as hearing a male actor say something – either about his per diem, or something else – and I was like, ‘Wait! Hold up – my part is way bigger than yours.’” No one talked about it in the early days? “Well, things have been designed so that we don’t.”

King has been a supporter of Time’s Up, the campaign to equalise pay and conditions for women in Hollywood. “That’s why this is a pretty exciting time. If I’m blessed enough to have a granddaughter, she’ll come in knowing this is how it’s going to be. I feel like it’s diminishing it by calling it a movement. It’s witnessing a shift, a life change. That’s how I look at it.”

It’s hard to convince people there is an audience that wants quiet stories

Crucially, she says, expectations have changed: there’s a suspicion that, just as sexual harassment will come back to bite you, so will pay differences. “No one wants their filthy past, their dirty little secret, to come out. A lot of people in these positions of power – white men – don’t even realise it was a problem, or something you should feel embarrassed about.”

King is glad she had a lot of solid success before she won the Oscar, playing supporting roles in big movies. “I’ve heard people say, ‘Oh, you were robbed with Jerry Maguire, or Ray.’ But I don’t think I would’ve had an appreciation for the art, in the way I do, if it had happened earlier.”

Beale Street was a different experience. “Oh, gosh,” says King, who found it so personal that talking about it still makes her emotional. Astonishingly, it was the first movie adaptation of a Baldwin novel, a film that remained a quiet, literary piece despite the starriness of its cast – and of its director, Barry Jenkins, fresh from his Oscar win for Moonlight the previous year. For King, who played Sharon Rivers, the mother of a young woman whose fiance is wrongly imprisoned for rape, it was everything: a love story, an indictment of the criminal justice system, and part of the vast, untold history of black life in the US. “We’re in a time when film is so loud and the audience is looking for shocking. It’s hard to convince people that there is an audience out there that wants quiet stories.”

Being in her 40s, she says, brings a confidence to go against the grain. She has started her own production company, vowing to staff all her projects with a minimum of 50% women. King wonders if she should have kept quiet about that, since she now gets asked about it every five minutes – and she has hardly hired anybody yet. “But at the end of the day, it’s holding my feet to the fire.”

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So does she feel in her prime? “For the most part, body-wise, I don’t feel different than when I was in my 20s,” she says. “Only when I hurt something, because it takes so long to get back. But the wisdom and regard for what’s important is different now. In my 20s, that I-don’t-give-a-fuck attitude is great. It helps you go out on a ledge and let your feet dangle down and not even think about it.”

Still, it is nothing compared with the thrill of having better judgment: “Being in your 40s and having the wherewithal to know, ‘Yeah, maybe not that ledge.’” She roars with laughter.

• Watchmen is on HBO in the US from 20 October and on Sky Atlantic and Now TV in the UK from 21 October.