Having written about immigration from the EU to the US, I thought I would turn the subject around and see what I could find out about American citizens residing in EU countries. I quickly discovered that this is a very tricky topic.
For one thing the American government does not seem to have a reliable system for tracking its citizens abroad. The US Census department considered including Americans abroad in the 2010 census and decided it was impossible. Only military and government personnel overseas counted - not private citizens. It is possible for US citizens abroad to register with the State Department or to inform the local US Embassy but this is strictly voluntary. In theory, US citizens everywhere in the world are supposed to file tax returns with the IRS but many don't. Voting records might give a clue but many who leave the US find it hard to figure out how to vote from abroad and just give up. (Tea Partiers take heart - all you have to do to be invisible to the US government is to leave the country.)
To complicate matters, the American population in Europe is very diverse and its citizens have radically different reasons for being in an EU country. Some US citizens in European countries are transient and have no intention of staying long-term: military and government personnel, tourists, students, professors, businessmen and women on assignment for their companies, people in the entertainment industry or the arts. Of the semi-permanent population there are international retirement migrants, spouses of EU citizens and work migrants. Finally, imagine the difficulty of determining the number of dual US/EU citizens who are living in one of their countries of citizenship in the EU and are not considered foreigners by that country and so do not appear in that country's statistics on immigrants.
Nevertheless, some organizations are trying. One source I found was the website of the Association of Americans Resident Overseas (AARO). They say that there are 5.08 million US citizens living outside the US (excluding military personnel) in over 160 different countries. About half of the migration (2.2 million) is to North and South American countries. Europe is a distant second with roughly 1.2 million. European countries with over 100,000 American citizens are: Germany, Spain, France, Greece, Italy and the UK.
Given that the EU has a population of nearly 500 million people I think it's fair to say that US migrants are a very small drop in a very big bucket. Nevertheless, our status is the same as any other migrant to the EU. We are called "third-country nationals" which just means that we are not citizens of any EU member state and we enter, live and work according to the laws of the EU country we reside in. Third-country nationals have limited rights in their countries of residence and almost none at the EU level. The EU is trying, however, to extend more protections to long-term foreign residents including the possibility of allowing permanent residents to circulate within the EU regardless of the member country where they first established EU residency. This directive passed in 2003 was one such attempt to protect the rights of all long-term foreign residents.
So a US citizen wanting live and work in an EU country must go through the immigration authorities for that particular country. Strangely enough I have met any number of Americans in France who are genuinely surprised that they have to go stand in line at the prefecture, speak to the officials in French (no, they do not generally speak English), provide the proper documentation and wait for the verdict just like everyone else. I don't want to poke fun at anyone's pain but it is deliciously ironic to hear US citizens complaining about the French bureaucracy and, in some cases, to hear their horror stories about trying to communicate with a French government official in a mixture of English and very bad French. One young gentleman I met recently admitted that it was a very humbling experience and that he now has much more empathy for immigrants trying to come to the US.
It's not easy to find precise and accurate statistics about how many Americans live in Europe and in what countries. I did find this site which combines data from AARO, AAWE (Association of American Wives of Europeans), ACA (American Citizens Abroad) and others. I can't vouch for these numbers but let's assume that they are roughly accurate. Here is their breakdown for EU countries that have large American resident populations:
Italy: 168, 967
France: 101,750 (I saw a figure elsewhere that said that 75,000 of these US citizens live in Paris)
If you interested in this topic (and personally I think it should be of interest to Americans at home and abroad) check out the Migration Policy Institute (MPI). They have good articles on both US and European immigration. From what I have read there is a fair amount of cooperation between the EU and the US on this subject.
I also hope that one day the US government takes a little more interest in US citizens abroad. Given that we are required to file tax returns in the US, it seems a bit odd that our numbers (5 million which would make us the 17th largest US state) don't count when it comes to Congressional seats. I believe that this is called "taxation without representation." :-)