That 20% residual you allow for seems to cause much larger problems for the major cities and sanctuary states who have to house, feed and provide medical care than such a negligible number would suggest.

Not really. Remember, folks who are awaiting the disposition of their asylum claims or other hearings aren't legally allowed to work (among other disabilities that come with being here without a visa) for a minimum of six months after entry, and for many even longer after that. Sure, some will be able to earn some money unlawfully in the informal economy - but there are limited opportunities there, so many (most?) will not be able to support themselves. It doesn't take all that many people in that situation to cause problems for the communities they land in, especially if they're all bunched up in their arrival.

The large number of migrants that came in during the peak did cause major problems. I don't disagree with that. I count the Administration's failure to recognize that as one of the three major political blunders they committed, and which have led to Biden's (and now Harris') problems in the polls against Trump. But that doesn't turn the number of migrants into ten million (when the entire population of the whole country hasn't increased by half that).