I've had good luck over the years finding clothes made in the USA. Usually it's by accident. I'll buy a dress made by Prana and it will be part bamboo (cool) and made here. I just happened to get the dress on sale. Or I'll be in Marshall's or Nordstrom Rack looking for new Yoga pants and the cheapest ones happen to be made in the US and of organic cotton.
Last week when I was in LA I had lunch in Malibu. I drove right by the American Apparel store on the PCH (Pacific Coast Highway). I decided to stop in because it seemed like a neat looking store. I remembered driving up that they make their clothes in LA. I wondered to myself if they use sweatshops or if they actually pay their workers fair wadges. As it turns out they do. I picked up some basics (tee shirt, tank top) and discovered much off the clothes were designed for a size 2-4 type frame (translation: if you're not super tiny, stick to the shirts versus pants and shorts unless you want your bottom to hang out). It turns out the tee shirt is one of the most comfortable ones I've ever purchased and it washes really well.
A great resource to find clothes made in the USA is found here. If you're looking for the American Apparel in the Boston area it's on Newbury Street. If you check out their website you will find things on sale for $10 or less. :)