[siedes]

>"Why wouldn’t we want to know the citizenship of the people living in the country? "

I think he told us that answer already. His politics benefits from noncitizens being counted in the census, so it would be problematic if such a question were to scare away any illegal immigrants living in the U.S (this is because no permanent legal resident is scared of citizenship questions, since it's usually clarified if something is okay for a legal resident noncitizen or not).