The point is, the increase in Covid-19 cases has nothing to do with the U.S. response to the “first wave”. It is about people who were infected in Mexico coming to the U.S. for treatment.
Your statement is true, but that was clearly not the point being made. Lot's of people coming back to the USA from MX and other countries. As long as they are US citizens or legal residents, we should accept them, and that is what is happening. How well we are screening them is another matter, but that is on CBP/DHS/CDC.