McALLEN, Texas (AP) — For about four months before President Joe Biden took office, advisers engaged in intense internal debate about how quickly they should undo his predecessor's hardline border policies.

The answer, almost always, was that Donald Trump's mark couldn't be erased soon enough.

Immigration advocates on the transition team defiantly shot down a detailed memo circulated among top aides that called for turning back some migrants who cross illegally by making them seek protection in other countries. They pushed back against estimates of soaring migration flows if Trump's policies w...