As a person living in Paris, I am not going to make judgment or value comments such as "Americans love money" or "Europeans prefer their friends" which in the end are not really measurable and are freighted with bias, if we are being honest.

To avoid coming off as a whinge, I would say that my family and I love living in France, and are happy to have made the choice to come here. The experiences are indeed different from what we had in the US (I lived most of my life in the San Francisco Bay Area, with about five years living just outside New York City). The pace of life is different; the type of housing is different. Attitudes of the people are different. Some of the differences are positive for us (I really like not having to drive, as we do not own a car, and take advantage of things like "Auto'lib" - something I guess similar to ZipCar in the US), some are negative (having your child get sick on a Saturday night and not being able to easily get access to acetaminophen because Monoprix is not Safewy, and thus not open after 8, and OTC meds are only available in pharmacies anyway).

But if you are seriously considering a move and not just looking to generate "the US is full of fat, religious troglodydes" 'answers', let me offer the following:

1) If you do not have a reasonable command of the local language, you are going to have a very, very difficult time living. Being a tourist in a city for a month is very, very different from living there. When our hot water tank failed, for example, getting a plumber to come and fix it would have been, at the least, difficult in English. Remember: shopkeepers along the Champs-Elysees can speak sufficient English. The guy who comes to repair a leak will not.

2) As others have said, be prepared to face difficulties "connecting" with the local people (here, I have to reserve my personal experience to France, where I live). One key difference between Americans and French - in my experience - is that casual friendships are not nearly so common. You almost surely will live in a flat with many neighbours, and they will already have a full set of existing friends and very likely, family. You will not be invited to parties or to dinner until you become real friends with them, which takes a lot of time. One odd thing - if someone has a party in your building, you likely will get a note - it's not an invitation, but merely a pre-emptory warning that there may be noise.

This is not to say the French are unfriendly - they just have different standards and rules around how you become friends. You may find this shocking.

3) Etiquette is very different, and you surely will run into at least one uncomfortable situation. There are certain behaviours in the country you move that the locals will just 'understand' intrinsically. At some point, you will violate one of these and get 'corrected.'

4) Rules - some of which that will make zero sense to you - will be enforced as if they were articles of faith. In the US, someone at the post office or in a local park may be willing to 'look the other way' if you are 30 seconds late or an application is not perfect. In France (again, my locus of understanding), civil servants observe the letter of the law, irrespective of the spirit. An intro to you will be procuring a "Titre de Sejour" (essentially, permission to live in France), for which you will need to submit forms and photos. Do not make a typo on the form, and make sure the photograph is *exactly* what the regulations call for. My wife's application at first was rejected - a delay of weeks and weeks - because she was smiling in the picture. The Prefecture de Police in Paris rejected because of that.

Imagine how you feel in the US when travelling at an airport, and having to submit to the exercise of shoe removal, belt removal, being asked if you packed your own luggage, and (my personal favourite - an incident that actually happened to me) having to put two tiny plastic bottles of shampoo (carried on) into ziploc bags because the rules said that they liquids needed to be in ziplic containers according to the TSA, as if plastic bags somehow act as a shield should the liquids ignite.

5) Culture shock. There are, as others have aptly said, many things to be said for life in Europe compared to the US. I won't go in to the pros and cons of food or art or lifestyle. But it's simply true that things are different here, and if you are not ready to deal frankly with the fact that you will HAVE to adapt, and not the other way around, then that is the best argument IMHO not to come.