Since Trump was right, and Schumer was wrong, you are trying to spin this like it's no big deal.
It does not surprise me that Trump believes he is more knowledgeable in this area than the WHO experts, and that you back him up in this belief.
It is a fact that travellers (both within and between countries) will tend to spread disease. It is also true that, as a new virus that is not yet firmly established in the general population, reasonable measures be taken to lower the risk of transmission of Covid-19. This includes restricting movement of people between hot spots of the infection and other areas, banning or limiting public gathering in areas considered at risk, surveillance of travellers, and contact tracing of anyone who tests positive for the virus. However, it should be recognised that blanket bans of people from countries that contain hot spots is an overreaction and that, if the economic costs of curbing travel are considered affordable, there are several ways that far more Americans could be protected from severe illness than just focusing on Covid-19.