The US was screwed by signing NAFTA (the North American Free Trade Agreement between Canada, the USA and Mexico beginning in 1994).
A bit of history: From c. 1950-1980, unions had a monopoly on labor supply in many industries. This allowed them to charge monopoly pricing, so employees gained a greater share of the wealth generated by their businesses.
With the opening of US borders to foreign trade (NAFTA was a part of this trend, but I mark its beginning with President Nixon's visit to China), elimination of most tariffs, and lower worldwide shipping costs due to improved logistics and technology, manufacturing became fungible between countries. So manufacturers largely relocated to other countries like China or Mexico with lower wages and laxer regulations.
I grew up in a manufacturing-heavy area that was economically devastated by these changes, and only now, decades later, is starting to recover. So I was exposed to the anti-free-trade position quite a bit, and I'm familiar with all its arguments; they sound convincing. And free trade's results look awfully poor.
So can anyone explain to me the incentives of free trade agreements from the US's point of view? Or if there aren't any, the political or strategic reasons they've gotten signed regardless of their drawbacks?