Hij is Amerikaans, would be in english he is American. For direct translation it would be wrong, but in Dutch you'll mostly hear hij is Amerikaans or Frans (French) or Duits (German). For professions can use both hij is een journalist, hij is journalist are heard often. For roles in familys, you mean like brother sister father? It will be said as "Hij is zijn broer" he's his brother " "Zij is zijn zus" she's his sister. Most times you leave the article when it's a adjective, and get a Possesive article or a indefinite article etc for professions or nouns.
You must be mistaken. I've only heard people in the U.S. refer to themselves as American. Only people from South America/Latin America are offended my the term American for people from the U.S. People fail to realize that this is a reference of country of origin and not continent. I don't go around Europe, Africa, Asia, etc., saying I'm North American.
Definitely not mistaken; I'm an "American" who specifically tries to avoid using that term whenever possible, but there's not really a word that means "United Statesian". This is unsatisfactory, however, because of how just saying "American" can offend people from other parts of the Americas.
I live in the Netherlands now, but I am American. I don't say "North American" When people ask where I'm from, I say America. They know exactly what I mean. I don't say I'm Californian unless I'm being really specific, and even then, people equate that with Los Angeles for a point of reference.