It was NAFTA followed by our trade agreements with Asia that effed us over. Instead of "opening foreign markets" it gutted our manufacturing base. Decent skilled workers were forced to work at lower wages because industry packed up and moved abroad. Suddenly McDonalds and WalMarx no longer had to offer anything above minimum wage to find employees. The minimum wage became government-mandated price fixing.
Normally that wouldn't be a huge problem. For every product people in the US import there has to be an export of equal price eventually. The reason why it's not quite that way with the US is that many countries around the world seem to believe that the US $ is not only a means to aquire goods essentially, but a product in and of itself that is worth having. They have little intention to trade them in for actual goods.
That being said, they are essentially just shipping you free stuff. It's a difficult claim to make that getting free stuff is that damaging. Yes, some of the jobs previously producing what is now being shipped in for free are going to go extinct. But these people can now provide the next urgent wants of others.
So there might be some transitionary damage to some people, but overall, and certainly over a longer period, that's actually a good thing. Unless other countries suddenly stop to demand dollars and want to trade in their money for actual goods when there is only a huge service industry that they can't use from abroad... but until then...