The soccer is trash and there's no support for it financially at the college level.
So to see matches at the highest level you have to watch European football. Also, Europe has all the personalities. RC7, Messi, Neymar are world celebrities. But we forget that players like Henry, Drogba, Ronaldinho (especially), and others were such great ambassadors for the game world wide and THEY were in Europe.
People DO stan their home squads, its just that MLS is so inorganic outside of the northwest. There's also no excitement brought on by the relegation system. Soccer structurally in America is just not that good.