EDIT: I see someone mentioning Trump below and I can’t reply. Trump was never interested in managing covid-19 or effective border control. This would’ve been the perfect opportunity for him to show why having smart borders was useful. He would’ve received support from within the government. He would’ve managed covid-19 successfully perhaps, and won re-election.
The problem was Trump was a completely ineffective and incompetent leader, who didn’t care at all about the things he claimed to care about. Mandatory quarantines and tests for people traveling to America would’ve been a lot of work and Trump was allergic to that. He was a man who preferred the cheers at his rallies over the difficult work of administrating and governing.