EU has very strong employee rights, so that will come to the same point as a union in the US. The lower pay is an advantage but the time zone difference of 8-12 hours can be a disadvantage. There are no language barriers in IT between the US and Europe, by the time they graduate college the average European has gone through more than a decade of English courses. Cultural differences are minor, management style is very similar (in the East) and so is the communication culture.
So yes, lots of American companies already outsource to East Europe. There are lots of "Silicon Valley"s across EE thriving on Western outsourcing from companies who aren't quite desperate or cheap enough to go to India.
There are some phenomenal outsourced shops in EE. Those that do pay 2-4 higher the going rate in the country. These aren't wordpress sweatshops. These are usually small teams and people work on interesting,specialised projects. Management style is usually very pragmatic ( a means a and let's cut the crap) .But the best part about these is that people do get exposed to things,build experience and eventually start on their own. 10-15 years ago there was hardly any product driven company in my country.Now the ones most worth working for do have successful software product that are sold in western markets.
So yes, lots of American companies already outsource to East Europe. There are lots of "Silicon Valley"s across EE thriving on Western outsourcing from companies who aren't quite desperate or cheap enough to go to India.