That explains a lot. I marvelled at how almost everyone, except for some elderly folk, spoke English in the Netherlands, and fairly American sounding English at that. I didn't understand about the dialects. I suppose all Dutch dialects are derived from German, though I wouldn't say that to a Dutchman to his face.
So is English. Especially obvious in words beginning with kn such as knee. In German (Kah-nee)the k is still pronounced but in English (Nee)it is silent.
In addition, I used to work in a prominent building in NYC. They invited many choirs to carol at Christmas for people visiting Santa Claus. Most choirs have very little to no accent. Especially notable, is the lack of accent in childrens choirs from what some consider "The Ghetto."
Did you happen to see the WW II movie, "Band of Brothers"? In one scene, the actor portraying the GI named Webster, in Holland was marveling at the Dutch. "They all love us, they all speak English ... ."
Just now, typing this, it strikes me how powerful the use of a common language can be.
Also knowing John Adams secured valuable monetary loans from the Dutch to the fledgling, struggling, almost friendless United States during a critical time in our Revolution (whether they spoke English at that time or not, I don't know), makes me have a special affinity for the Dutch.