USA people have been installing themselves as workers all around the world for many decades, including the present one (hey, just check with Mach if you need a sample). Most often in the highest paying jobs, too. So it's hardly suprising that other countries also export workers, often to the USA.

Moving large numbers of jobs overseas is somewhat different -- often this is done to put the design/production closer to the largest customers (eg. China). Another big factor is that the USA *is* very wealthy, and nearly all of it's citizens are too, on a world scale. They don't live in mud huts, and rarely have 10 people to an apartment or single room. As such, they're not willing to do basic labour for really cheap pay. Other parts of the world are not so well off, and are more than happy for the work.

Cheers