This will be a mess. There IS NO national, comprehensive list of who is a citizen. The closest seems to be the one that DHS has, but that is woefully incomplete
The country has gone for 250 years with the current (more or less ad hoc) system. And suddenly it's a raging panic!!!
When Trump loses Congress this year (most likely will) we will be subjected to another national temper tantrum because 'the whole country loves Trump'