(Is it a common term in American usage? I had it in my head that it's a Britishism).

I've heard it in the U.S. pretty much my entire life, but I think of it as strongly British. I would not have said it was in common usage until relatively recently; I also feel there's been a recent shift from the specifically sexual sense to the more generally derogatory, which may or may not reflect the way it's used in the UK. Is the person on your friendlist American?

45 seems a better strategy to my mind.

It's unambiguous and succinct.