Speaking from a US centric view, the only way to protect America is to control the disease at it's source. If you prevent air travel, you make it difficult, if

Speaking from a US centric view, the only way to protect America is to control the disease at it's source. If you prevent air travel, you make it difficult, if not possible to control the disease. By putting on travel restrictions, you will lose control of the disease and jeopardize the United States. So, in effect, if you wanted to spread the disease and put the United States in grave danger, you would put travel restrictions in place.