In a decision that promises profound lifestyle changes for million of Americans, the Supreme Court on Monday ruled that the national ban on sports betting is unconstitutional.

Ruling 7-to-2, the Court ruled in favor of New Jersey in its years long battle against the four major sports leagues — MLB, NBA, NHL and NFL, each hell-bent on stopping sports gambling from expanding essentially beyond Nevada.

“Just as Congress lacks the power to order a state legislature not to enact a law authorizing sports gambling, it may not order a state legislature to refrain from enacting a law licensing sports gambling,” Judge Sam Alito said in his majority opinion.

New Jersey, through a 2011 referendum and 2014 law, legalized sports betting at casinos and racetracks. That law will now go into effect — and sports bets could begin being accepted before the end of the month, or in time for the NBA Finals.

Monmouth Park, about 55 miles south of Manhattan, plans to open a sports book in about two weeks, and offer mobile sports betting soon after.

New York is not far behind.

Empire State voters in 2013 approved a referendum that allowed casino expansion, including the right for four new casinos to offer sports betting.

Now, the New York legislature needs to enact a law to define what sports betting is allowed, and the New York Gaming Commission needs to license the four casinos to take sports bets.

State Senator John Bonacic (R-Catskills) told The Post he plans to introduce a bill next Monday to the full Senate and have it enacted into law by June 20, when the legislature takes it summer recess.

Bonacic’s bill calls for mobile sports betting, and for sports betting kiosks in racinos at Aqueduct and Yonkers racetracks. While neither Aqueduct nor Yonkers can run sports books, they will be allowed to let the four casinos operate sports books at their facilities, he said.

The executive president of Resorts World Catskills (one of the four licensed casinos), Charles Degliomini told The Post, “We are ready to go as soon as the regulatory environment is complete.”

Degliomini said Resorts World can convert its large sports bar into a sports book in about 30 to 45 days.

He said his goal is to offer sports betting before football season starts.

Degliomini also said he is close to choosing an experienced sports bookmaking company to run its sports book.

There are no short term plans for sports betting in Connecticut.

By repealing the Professional and Amateur Sports Protection Act (PASPA), the Supreme Court opens the door for any state to legalize sports betting.

Congress can still enact a law to stop sports betting — but would likely have to do so across the entire country, including Las Vegas, where it has been legal for decades. PASPA allowed sports gambling in Nevadas and three other states.

At the Monmouth Park racetrack, just an hour’s Uber ride from Midtown, a 300-seat sports book operation promises to be open for business in about two weeks, its chief operator Dennis Drazin told The Post.

New Jersey plans to craft a new law that supersedes the 2014 law but Monmouth does not need to wait.

Bonacic said he is projecting New York will collect roughly $30 million in taxes from sports betting. Former New Jersey State Senator Ray Lesniak says his state will collect several hundred million a year from sports betting.

Other states will also be working fast on passing legislation which has already been drafted.

“You have a handful of states that could move immediately,” said Chris Grove, Managing Director at the Eilers & Krejcik Gaming research firm. “That includes Pennsylvania, West Virginia, Delaware, Oregon and Mississippi.”

“Another group of states would move very quickly,” he says, including Illinois, Massachusetts and Michigan.

If sports betting were to be legalized in all states, Grove said there would be roughly $300 billion wagered annually.

To compare, the money wagered in casinos would still be four or five times larger than what is wagered on sports betting, Grove said.

Meanwhile, not everyone thinks legalizing sports betting is great news.

Certified compulsive gambling counselor Arnie Wexler, who for six years ran the responsible gaming program at Donald Trump’s Atlantic City casinos, said he believes the number of gambling addicts will greatly increase.

“Some people that would never place a bet with a bookmaker because it is illegal will now start betting.”

“The bottom line is this will be a real disaster,” Wexler said.

Supreme Court Justice Ruth Bader Ginsburg, in her dissenting opinion, said the Supreme Court should have let parts of PASPA survive.

“The relevant question is whether the [US] legislature would have wanted unproblematic aspects of the legislation to survive or would want them to fall along with the infirmity.”