Globalization is the #1 cause of the decline of manufacturing jobs in the US. Blame Bush, Obama or anyone else you want to.
Eliminate oversea tax shelters? Bullshit. If the US tax code was fair companies would bring that money back to the US in a heartbeat. I read today in the WSJ over $1 trillion is sitting the oversea accounts for US corps and they will not bring it back. Why? They have to write a check to uncle same for 30%+ of it. Who in their mind would do that?
Also, if you are running a multinational corp, and your competition is kicking the shit out of you, what do you do? You go to the place with the most cost efficient labor market and a location with favorable taxes. Ireland lowered it business tax in the 1990's and companies invested tens of billions of dollars in that country. The US could do the same.