I'd say that the biggest advantage of shooting a porn movie in Eastern Europe as opposed to USA is that you don't have to deal with US travel restrictions for foreigners, who want to work in USA.
There are no restrictions for US citizens travelling to Europe to create work for Europeans, but Europeans going to USA to do some work in USA can be a big problem. Because foreign employers are usually welcomed, but foreign workers are often shunned, banned, and excluded in most countries, including USA.
I don't know much about making porn movies in Eastern Europe. But making such movies is probably easiest in countries where prostitution is legalized. Because porn-making is having sex for money and filming it too. In USA, porn-making isn't considered prostitution. But this is just legal hair-splitting and a legal loophole allowed by US politicians for business purposes. Governments in other countries might not see it this way.
http://en.wikipedia.org/wiki/Prostitution_in_Europe
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