I’m currently wearing my athletic socks and they’re black. They came in a multi pack with blue and grey. My casual socks are grey and blue as well. My formal dress socks are black. I’ve got a few pairs of brown work socks.

Thinking back, I can only remember one time when I had white sports socks (tube socks with the red and blue bands at the top) and that was in the early 1980s.

My guess about the US and white socks is that they were mass produced for football and baseball (and basketball) and they made the migration to casual wear alongside running shoes, because people could pick up both item ms affordably in the same store (K-Mart and the like).