The World Cup, the most popular sporting event in the world, has surpassed a cultural milestone U.S. cynics never thought possible: It has officially won over American fans.

It helps that the U.S. squad has performed well on the pitch, brushing off predictions of an early demise to advance to the second round in Brazil. But as much as in-match successes have fueled the Americans, it's the growing number of World Cup viewers that could push the sport into the echelon of football, basketball, baseball and other events that consistently draw more viewers in the U.S.

The nation's relatively few pre-2000 soccer fans have long been saying this day would come. Now it has. Take a look at the numbers: The U.S.'s thrilling 2-2 tie against Portugal (yes, a tie can be thrilling) was watched by 25 million viewers, according to Nielsen. It is the most-watched soccer match in U.S. history.

While that's nowhere near viewership numbers for even the most-dreadful Super Bowl, it more than holds its own against the NBA Finals (15.5 million average), the 2013 World Series (almost 15 million) and Game 1 of the recent Stanley Cup Final (just under 5 million).

On Thursday during the Americans' 1-0 loss to Germany (remember, they still advanced) some users of the mobile app WatchESPN actually had trouble streaming the game because of unprecedented demand.

Is soccer poised to unseat one of America's major sports? Probably not. But no one can honestly call soccer a "niche sport" anymore.