A litany of jobs? Do you mean a minority of jobs - civil service, some clearance jobs, holding some offices?

The Immigration and Nationality Act makes citizenship discrimination illegal.

>Other countries get by just fine

Which ones are your model for the US?

Oh, spare me. What an unserious statement. The entire point of an I-9 is to discriminate on citizenship, which is the document that HR pesters you on for your first few days at any new job anyway.