Re: nouns of multitude + verb
Even with the BrE use of the plural for a team, it would still be "the champion" though, right?
In the US, you'd use "is" for the US. It's a single country.
With teams and bands, it's a big odd - we tend to use the plural if the team name is plural and the singular if the team name is singular. The Spurs are a good team. The Heat is a good team. But people are not consistent. The Beatles were great. Heart had a song called "Barracuda."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.