I'm currently rocking a Xiaomi in the US. People do import them and sell them here and it's pretty good. But it won't be problem free. Some carriers which do IMEI whitelisting might give you a hard time (Verizon did, ended up going with t-mobile), for me visual voicemail doesn't work, and it wasn't all that great of a deal. Most of all though, you need to look at what network bands they support and what your carrier uses or you'll frequently find yourself with poor connection. Fortunately, many of the current Xiaomi models have pretty good network compatility with T-mobile it seems. I used this site.