Actually, most US games are region-free. If you're unsure about a game being region-free or not, check www.videogamesplus.ca. They have a lot of international customers, so they test basically every game they get.
Been ages since I last saw a region-locked US 360 game. On top of my head, I can only remember Tales of Vesperia, Lost Odyssey and Eternal Sonata, but there are more.
This is a semi-non issue anyway, as most games gets an Asia release with English voices and English text/subtitles, and they're usually cheaper than games bought in North America. Downside is that Play-Asia becomes your only option, but I remain firm on the fact that most NTSC (US) games are region-free.