A Dutch friend of mine speaks absolutely flawless English with an American accent - I honestly thought he was American when I first heard him talk. He says he learnt English when he was in the army and spent time at a base with American and British soldiers, but that his accent does mostly come from watching American TV shows and films. Another Dutch friend, who is fluent but has a definite accent and learnt English at school, doesn't sound American at all.
I have worked with a number of Dutch people. All of them had a noticeable accent, although it was stronger in some than in others. None that I can recall had an American accent.
When I worked in Spain, the only person I can remember who was neither English nor Spanish, but spoke both languages without a noticeable accent, was a German. He was very intelligent and well-educated, and also a very nice person.