I should think privileges of citizenship would be affected, if such a requirement were in place. There would have to be a curve, for a person’s ability to comprehend, and/or express knowledge of some things. Probably voting rights would be withheld, entry into some organizations, and maybe a difference in taxation. More extreme would go to ownership of property; land, and none essentials. Boats, RVs, and other big ticket items could be owned only by licensed citizens.
Maybe those who opt out of the test could earn their citizenship (As some immigrants do) by serving in the military.
Hmmmmm.
I’m proud to be a citizen, and know things like; there are the same number of states as cards in a standard poker deck.