Devices in the US will be sold in carriers stores, as well as at Microsoft Store locations and Amazon. Here is the launch lineup that we will see in the USA in time for the holidays:
T-Mobile ends up with the largest phone in the HTC HD7 and since they are the carrier I have I am excited about getting this high end device. T-Mobile USA also looks to be the only carrier launching with a Dell model Windows Phone 7 device. It looks like both of T-Mobile's devices are targeted towards the high end while AT&T looks to have a full range of product offerings.
The HD7 will also be available from other carriers around the world and it looks like the USA is missing out on the Samsung Omnia 7, HTC Mozart, LG Optimus 7, and HTC Trophy.