equating skin colour with culture

Not equating. They said that people of an ethnicity are often also of a culture common among those of that ethnicity.

I’m in Costa Rica, and people are likely to (correctly) assume that I’m a foreigner here because I’m white.

It’s not equating. It is, however, a way to tell what is likely.

Bring any nuance to a charged topic and the ones who think in black and white terms will come to misinterpret what you said in the least charitable way.