Certainly its popularity has grown here in a few ways. Here's how I see it (my subjective opinions only) based on living\playing in a few different areas across the USA and also being alive in the USA since the 70s. To varying degrees I see the rise in popularity on US TV due to: 1) the hispanic community has gotten more integrated into neighborhoods they live in and their presence has resulted in organizing leagues as well as recruiting non-Hispanic players into their leagues (this is a shift across time as leagues in the 70s were far more insular than leagues in the 2010s); 2) the game is generally an easy, relatively inexpensive-way to allow surburban parents have "an event" to encourage their kids to join when young (relative to US football, hockey, baseball--you basically just need good footware) so this has encouraged many upstart leagues for a new generation, including the inclusion of recently integrated Hispanic families into what were largely formerly white communities; 3) independent of whether you have played the sport, there is currently a minority but market-formidable hipster attitude in the US to be anti-establishment, and this means, for whatever it's worth, to shun mainstream sports (and beer companies) and to embrace "global" sports; and the fact that matches do not have repeated interruptions of TV commercials has also attracted appeal; 4) the USA has been exemplary in developing the women's game, which has resulted in an increased enthusiasm for the game in general (subjectively, pub attendance for women's and men's World Cup games have been about the same over the last 3 world cups for me); and, 5) as a result 1, 2, 3, and 4, there is an increasing presence of USA citizens who view soccer as their "go to" sport and have found an expanding community of fans to share their enthusiasm with. And TV markets have responded.
Back in the early 80s, to be frank, the idea of soccer being mainstream in the USA was touch-and-go. Among other things there was the quality of play--still debateble relative to international terms, and flying teams 6 hours across to the country to play in a match was, and is, economically problematic. But I think we've turned a corner and soccer is here to stay. The quality of play in leagues has improved and also there are now established fan bases in many regions.