Most don’t care about citizenship. Most don’t care to assimilate. They just want to work and send money “home.”
It sends a bad message - if you can get to the US by any means, eventually they will let you stay. When that happens, we no longer control our own immigration.
It is also dangerous to have two classes of people. Citizens that can vote and “others” that we allow to live here but not participate in the American process.
Enforce current laws and most will self deport.
Many societies have done passably well with 2 or more classes of residents. Not that we need to do that, but classes, in and of themselves, are not a cause for concern.