I think Dutch people can’t place your accent not because they’re not used to hearing Dutch spoken with a foreign accent. It’s not a very popular language to learn. And (I am assuming) you don’t look Asian so they can guess “Indonesian” or whatever.

I get a lot of Dutch people who think I am South African or German. Is it because I sound like either of those accents? Nope. It’s whiteness. Sometimes I pretend to be Romanian (or whatever they guess that time) just because I am bored, and stopped giving a fuck a while ago.

Im not saying that to take away from your Dutch skills. I also speak very fluent, very technical Dutch (and work in Dutch)- I’m just speaking from my experience