I root for the USMNT at the World Cup, though I don't follow it much. The ESPN highlights of about 3-4 minutes per match are just about perfect for my interest, even though all my sons player soccer and one had dreams of playing professionally. It's a lot of fun to watch live.
Who do you root for second? I think in international play I tend to root for Canada next in most sports. Because of Swedish heritage I used to root for them at the Olympics when I was a boy, but not so much now. I have a son in Norway, I root for them at times. If the Romanians are in the mix I root for them, less so the Hungarians. As an Anglophile I will root for England, less often Ireland/Wales/Scotland.
It's an odd collection after that. I don't dislike many countries, after all, and still tend to be an underdog rooter. If a Caribbean country sneaks its way into something international I perk up over that. Countries that have seen hard times, like the former Yugoslav states or many African ones I will watch that. South Sudan especially.
Who else do you like out there, in the World Cup or more broadly?
BTW, NPR really missed a trick decades ago when it did not adopt World Cup coverage as an important part of its programming. They could have had the rights for cheap; it fit their internationalist, junior-year-abroad, sophisticated, not noisily-patriotic appeal; they could have tied it to other things. They had the chance and they missed it.