The accent is really usually more of a Dutch accent than it is an American one, though I guess that's closer to the American one than to the British one [1]. I'm not sure if it's been researched, but what would seem to be the obvious reason is that we just hear a lot more spoken American English than British English, on TV, on the radio, and online.

[1] If you don't mind TikTok, this is an interesting comparison: https://www.tiktok.com/@rogierbakcomedy/video/69224330661409...