I was disappointed Harris didn't pick up on an offhand comment from the moderator about what it would look like to deport millions of undocumented immigrants, "Would you go door to door?"
Because there isn't some massive immigrant city you can clear out. They're baby sitters, home care providers for the elderly, gardeners (and hotel maids in Trump's properties). You aren't going to find them unless you check everyone's homes.
Lots of checkpoints and arbitrary traffic stops for starters.
And White people need to be aware that there will be lots of people who were deported to Ireland or Canada or lots of other places where White people come from, and if you've got the same name as one of them, you're going to get detained, too.
My brother has the same (common) Irish name as an IRA terrorist, and he had to leave extra time at the airport every time until he could get Trusted Traveler.