Belgium and the Netherlands, so close but so different

I did a lightning trip to Amsterdam yesterday, and was really surprised at the slight but definite changes at the border between Belgium and the Netherlands, even though they're both part of what is generally defined as the Low Countries and I had made the same trip before. Below some that I could think about:

• Languages: Suddenly people only speak English and Dutch in the train, German and French disappeared (except for the tourists, of course).
  
• Landscape: Much more channels, bridges and water surrounding you.
• Infrastructure: The train stations look newer. Funnily enough, they also look somehow dirtier.
• Architecture: We went past a few windmills, and there are some definitely distinctive elements of architecture that are not found in Belgium. Brussels is more Frenchified, the Netherlands looks somehow, well, I don't know how to explain it... German/Nordic maybe? We also passed in front of a couple of mosques.
  
• Bycicles: I expected that to be part of the Brussels landscape, but it isn't. In the Netherlands in general but in Amsterdam in particular bikes are everywhere.