What's some cool minimalist but significant bits of world building?

A lot of our worlds are maximalist: custom solar system, magic system, races with different anatomies....

But I'm trying to think through the smallest changes that have impact.

Examples: in ASOFIA, GRRM has seasons that last for an indeterminate number of years, not exactly three months. This has all sorts of interesting ripples effects to how people think about the world ("oh, my sweet child of summer", "Winter is coming.")

The other one that we see often is a time travel / alternate history, so what if WWII ended differently (e.g., Man In the High Castle, Wolfenstein), etc.

Or, real world but magic exists, but only a certain subclass can see it.

I'm trying to come up with a few "everyday but a little bit of magic" scenarios for a story I have in the back of my head.