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.
The pronunciation is a bit off, the stress should be placed on -aan: ameri'kan