They can only really effect the American sales. MOst apps sell a very sizable percentage overseas (I've seen about 45%, I've seen other devs with more like 60-80% overseas).
I only develop on Android at the moment, and sell in the Android Market, and if I limited sales strictly to overseas, I'd be dead in the water. ~80% of all my sales are in the U.S.
iOS is a much deeper base more willing to pay. It's worth the cost of a mini or air, and would also happen to safeguard you against patents more (Apple's already batted down lodsys for instance).