Finnish has a word for "USian", yhdysvaltalainen (the name of the country is Amerikan yhdysvallat or Yhdysvallat) but it's a bit formal, in every day speech it's usually amerikkalainen (or even jenkki, Yankee). That only refers to people from USA usually. The country is usually USA, even though it's not Finnish, it's pronounced as a word instead of an abbreviation (sort of like oo-sa). You can even say usalainen. Oh, merciful heavens, don't call us yankees!
Don't worry, I won't
Jenkki is rather neutral here and it's used to refer to all sorts of things that are thought American, often in a sort of stereotypical 1950s rock'n'roll way that probably has nothing to do with real America. So there's Jenkki chewing gum, jenkki beds (it has two mattresses on top of each other), jenkki hair (a crew cut), jenkki fridge (it has a small freezer on top of the fridge while more often fridge freezer combinations have the freezer on the bottom and it's as large as the fridge), jenkki auto (not just any American car but this sort
) and so on. Jenkki used for people can be derogative (it's often used in relation to wars and things like that) but it's not used that much, at least in person as most people have very little to do with actual Americans (our biggest group of tourists is Russians).
We have a word for holidays, pyhät or pyhäpäivät or juhlapyhät, literally holy days, even when they're not religious (but most of the official holidays are, apart from Independence Day and May Day) but I can't really imagine using that word to say that I like to get together with my family over the holidays. Many people spend the holidays with their families and it's expected but I wonder if the difference is that it doesn't require much effort so there isn't really a concept for that. I live quite far from my mother but it's still only three or four hours by train so getting there for Christmas is rather commonplace. Many people will travel longer distances and being with your family is seen as important but I guess it's not something people will often say (but if you want you can say "Vietän juhlapyhät mielelläni perheeni parissa."). I also wonder if holidays seem to be more important to Americans because you have less vacation time? Or at least that's my impression, in Finland it's common to have six weeks of paid vacation time a year.
I'm sorry to bring my language to a discussion about differences in English but I can't seem to stay away.