Yeah, I love soccer and saw the second-ever MLS Cup live at RFK Stadium, but it's not that popular in the US. There's certainly an audience and a market that wasn't there before, which is helped by high level European club soccer being available on cable.
But it's not close to the NBA's popularity, and is probably still behind the NHL. Also, it's not the EPL and La Liga that people follow as much as the Champion's League and the select clubs that regularly qualify for it. You see lots of Man U, Arsenal, Barca, and Madrid kits but not so much Stoke and Osasuna. The CL is becoming more and more a default top league for Europe, and it'll be interesting to see whether it becomes more and more autonomous as time goes on.