I think directly calling it the colonizer mentality is more effective.

Don’t sweat it. It’s pretty widespread language and its hardly your fault we are saturated in these things. Certainly your point stands.

I think “us vs them” is difficult because sometimes it is brought up to say “we are all in this together” or such things, which is not always the case, or at least it is more complicated than that. It can be used to disregard, oversimplify, or otherwise unfairly delegitemize polarity that exists as a way of ignoring opposition. Like with climate change, it is mostly the doing of rich capitalist countries so it is probably ok if the global south makes that distinction known.

Of course this is not to say we should be “othering” people. You probably don’t need me to tell you any if this tho I’m just blabbing.

I might call it colonialial mentality like was mentioned. Or maybe racism, or orientalism. Europe has done a good job of failing denazification so you could refer to it in that light as well.