I mean, obviously there are some in the US who follow it, I was only just discussing it with Greg in another thread, but you wouldn't think it's mainstream enough to release an American movie about it. Unless they're hoping to aim it more at the European market than the American one, but that would be pretty rare for Hollywood movies...
I might watch a Eurovision movie, but I'm really not a Will Ferrell fan and from your review doesn't exactly sound great. Though as you say, you may not be the best placed to judge.
It's mainstream enough among some subpopulations in the US. Gay men for instance. Rachel McAdams is in it also and she tempers the annoyingness of Ferrell.
Ultimately its a movie made by an American who loves Eurovision. And it shows. Even if the facts are not always right. Or the urban geography.