And even in the UK we're not consistent. I would say Aaron is Air-on. If you want it to rhyme with Karen, it's spelled Arron. Different name. And Erin is Air-in.
But I agree with you about Colin Powell.
I've mentioned before, I wince at Caitlin pronounced Kate-Lynn, because where I come from it's Kathleen, or possibly Cashlin. I tell myself it's different other places. I don't know why that one annoys me, when other name variants don't.