Don't you think that has to do with tradition? Must of the first Football teams was something FC, in Englanf, or germany or france it is FC. And when Football (soccer) started to grew in the states they just followed suit.
That makes as much sense as anything. I suppose it's a way to keep the European (or international) flavor, which is something a certain kind of American simply adores.
I was watching a documentary about the film,
Birdman, a couple weeks ago and there was a bit about the crowds on Broadway reacting to a mock-up theater sign for Riggan Thompson in
What We Talk About When We Talk About Love. A fictitious actor in a fictitious play. The joke was that passersby -- not involved in the filming -- could be heard to remark about the sign.
Lady: "Hmmm. Riggan Thompson, he looks familiar."
(Of course he looks familiar, he was Batman)
Lady's Friend: "Oh yes. I've heard of Riggan Thompson, I believe he's British (which automatically makes him interesting).
What was it Mark Twain said about foolishness and opening one's mouth?