Well, I just explained to you why your comment about no one denying race was a social construct still leaves you having to deal with real underlying biological groupings.
You ignored that. The queries about the other groups brings up the acknowledged reality that there are mixed zones in humans just as there are in other sub-species and races . In the context of that Time article they are referring to the UK, Germany & US as being predominantly caucasion. Who do you think they are referring to? People whose ancesters were born in Europe.
If you do a search on Google Scholar you’ll find the term caucasian is commonly used, particularly in relation to health research. The term generally isn’t even defined because it is taken as self evident - for example in NZ caucasian simply refers to those whose ancestry is from Europe.
I’m not sure if this article by Leroi can help clarify the point. Anyway dude, I will be back in a few days (am away with family - so will try to address your queries further then).