You guessed right with the economic migrants. Americans aren't the only ones doing it, though. In Europe, it's primarily the British moving to Spain and Portugal, but others do it, too.
In terms of trying to influence local customs: this ranges from very blatant (canvassing or campaigning in favour of socially conservative causes) to seemingly innocent, but so common that people are annoyed about them even more (trying to introduce American tipping culture to pubs and restaurants). Usually the best people in this regard are well-traveled Americans who already lived abroad. Of those, by far the best adjusted are children of former military personnel stationed abroad.
I think this is just for fun. However, I did work for a company where we did everything in-house from scratch, down to our own font face, because we couldn't afford the legal costs associated with deciphering license agreements.