(CNN) The US women's national soccer team won their second consecutive World Cup because they were the best team.

United States women's soccer team member Megan Rapinoe holds the Women's World Cup trophy as she poses for the media after arriving with the rest of the team at Newark Liberty International Airport, Monday, July 8, 2019, in Newark, N.J. (AP Photo/Kathy Willens)

But their all around fabulousness as one of several successive generations of American women dominating the sport has its roots in a law passed in 1972 and signed by Richard Nixon. And that means their fight for pay equality is the latest important step in an ongoing and very, very slow walk toward gender equality.

The news today is their effort to force the US Soccer Federation to pay its women the same way it pays the men. Given the amount of public support and political pressure, there's very little chance the US Women don't emerge with pay equal to the US men in short order through arbitration.

If that doesn't work, Sen. Joe Manchin, a West Virginia Democrat, wants to keep the federal government from funding US efforts to prepare for the 2026 men's World Cup until the women's team receives equal pay. A bolder plan might be to make the same demand of FIFA, which only held the first women's world cup in 1991.

But an important first step came when Nixon signed The Education Amendments of 1972 into law. That law included Title IX, which banned discrimination on the basis of sex at schools receiving any federal funding. It might be better known today for the way it has changed how colleges deal with allegations of sexual assault.

Accidental impact

Its impact on sports is something of an accident. Coverage of the signing of the Education Amendments of 1972 that June was dominated not by sports or even parity in college admissions, but by the issue of busing.

Nixon groused that the law did not do enough to cut down on the busing of minority children. Nixon signed the law but vowed to push an anti-busing constitutional amendment. The fact that Nixon was willing to hold his nose and sign a bill he didn't particularly love is striking in today's zero sum political climate.

It became clear pretty quickly that not allowing discrimination on the basis of sex was going to have a huge effect on college sports, but Congress pushed back repeated and successive efforts to exempt sports from the law, to exempt basketball and football from the law and more. Players who were cut from male sports like wrestling and track and field in order to make room for women's sports, while keeping football programs, sued and lost in 2004

Those efforts eventually died out and now -- decades later -- more women are playing sports and more women than men are going to college. Colleges today are actually trying very hard to get more men to go to school to find parity in the other direction.

Impact around the world

There's been an explosion of women in athletics since the passage of Title IX. And particularly for women's sports, it's had a worldwide effect.

According to data from the NCAA, all but nine of the 24 teams competing at the World Cup had at least one current or former player who played US college soccer. That includes three teams -- US, Canada and Jamaica -- where most of the roster competed at a US school. Two US players -- Lindsay Horan and Mallory Pugh -- skipped college

At the Summer Olympics in 2016, 168 then-current NCAA athletes competed-- 92 were women and 76 who were men, according to an NCAA list

Less than a quarter of the NCAA athlete women were competing for the US, compared to 38% of the men. That suggests US college sports have an outsize impact on women in international sports.

At the same time, college is becoming less and less a feeder system for men who play soccer, and the college format of playing for a relatively short season has been cited as one reason that American men are not as good as players from other countries. That's changing since fewer male players are going to college.

A growing percentage of top men's players play with youth development teams and sign professional contracts out of high school. A review by Stars and Stripes found that half of the men who played on the US national team from 2008 to 2018 took that route.

That's also the model for top talent in men's basketball, where more elite players are entering the draft as soon as they possibly can or playing in the NBA G League where they can be paid a salary.

Those salaries aren't available to women, and until there is a consistent fan base for women's professional sports, there won't be.

Different leagues: NWSL v. MLS

Unless you've been under a rock, you know the women's team won the World Cup over the weekend while the men's team lost in the final of the North American regional tournament -- the Gold Cup -- to Mexico.

Players for the US men's team will lick their wounds from a dispiriting loss and return to fat salaries at club teams in the MLS, England's Premier League and Germany's Bundesliga.

All of the US women, meanwhile, play in the domestic NWSL, where the league maximum salary for non-national team players is less than $50,000 per year.

The league's salary cap of $421,500, spread across a 22-player roster , is actually much lower -- $19,159, less than a living wage -- although teams can also give money to help players with housing and transportation. Those figures were not disclosed by the league.

The league minimum salary per player in the MLS is more than $70,000 and multiple players make multiple millions of dollars per year.

The NWSL has only been active as a league since 2013, although there were predecessors. In contrast, MLS has been growing for 23 years and expanded.

This is something that will change if the NWSL takes hold in the US along with women's professional leagues in Europe and elsewhere. Supporters of the US women's political statements might do well to head out to a North Carolina Courage or Washington Spirit game, and support them there too.

More boys are still playing sports than girls. According to an NCAA report prepared for the 45th anniversary of Title IX, 58% of high school boys (about 4.5 million) were participating in sports in 2016. That's compared to 42% of girls (about 3.3 million).

But that's a dramatic increase from the 7% of girls who took part in a high school sport in 1972. Today, about 6.5% of high school female athletes will go on to a play college sports, compared to about 6% of high school male athletes.

There has been a growth of opportunities for women in so many elements of US life. The Congress that voted to create Title IX had 17 women. If the US women's national team visits Congress as part of their victory tour, there will be 127 . That's far fewer than half the 535 congressman and senators, however.

The next frontier of gender in sports may very well be how to include trans athletes.

That's a conversation that's also been going on since the 1970s, when Renee Raskin became the first trans athlete to compete in professional tennis. There are two trans women in professional golf