The Ural mountains, the Black Sea and the Bosporus aren't sensical physical boundaries?

The term "North America" almost always means US or US and Canada, hardly ever the technically correct "US, Canada, Mexico" except in things like NAFTA.

And "Central America" often means "Mexico and countries south that speak Spanish" even though LATAM might be a bit closer.

The traditional boundaries of Asia were Bosporus and Nile. Europe, Asia, and Africa were names given to the lands surrounding the Mediterranean. Because sea enabled travel, while land was difficult to cross, the extension of those names to lands beyond the Mediterranean world was of little consequence.

Not really. there is no entirely accepted definition of a continent. If you want to refer to them as one continent the term is Eurasia.

> There is no reason to separate Europe out of Asia except for that "people that look like that go over there."

People that look like what? A lot of west and central Asians look far more like Europeans than like South Indian or Chinese people, and the latter resemble two do not resemble each other at all.

You cannot put it down to racism dividing white vs non-white because that is very recent. It predates the invention/introduction of racism to Europe. Even better, until well into the 20th century (literally millennia after people separated Europe from Asia) South Asians and some North Africans were regarded as belonging to the same race as Europeans: https://en.wikipedia.org/wiki/Caucasian_race