“How can non-citizens be counted for the purposes of representation?”
The Constitution does not differentiate between citizens and non-citizens and the provision for the census only requires that all persons be counted. Right now each congressman represents about 690,000 people. California with its millions of illegal aliens, gets 3-4 additional representatives because of them. Texan and Florida and New York also get more representatives because of them.
Must also include visitors, tourists, hitchhikers.