There are bureaucratic hurdles for some of the really good stuff in the U.S. Standard handguns, rifles, shotguns, semi-auto assault rifles, etc. just require a background check -- at least here in Texas. You don't even need a license to carry in your vehicle.
You have to set up a gun trust and go through the ATF to get the fully-automatic stuff and sound suppressors, though. There's a gun shop near my house that sells full-auto and silencers. They also rent out the fully-automatic stuff for use on their indoor range. $60 an hour, plus ammo ... and you can rotate weapons. MP5s, Tommy guns, AK-47s -- the whole nine yards.
Haven't gotten the opportunity, yet -- but the guy next to me last time I took my Kimber and P30 to the range was mowing through tommygun ammo.
SnakeDoc