I just did some back-of-the-sleeve calculations on the incidence of Corona-infections in the US which make me wonder which continent is protected against which

I just did some back-of-the-sleeve calculations on the incidence of Corona-infections in the US which make me wonder which continent is protected against which by this travel ban. My source of information is the video reporting by Dr. John Campbell [1] who thus far has been one of the more level-headed sources on the ongoing pandemic. Here goes: The official number of cases in the US as reported by Campbell is 1084, with 33 dead. This number roughly tallied with what I see on the CDC site (they report 938 cases, 28 dead) [2]. The major of Seattle estimates there around 1100 infections in this city (source: Campbell's video), a number which could grow to about 70.000 in 6 weeks (source: Campbell's video, most likely based on the spread in Wuhan) Seattle has a population of around 750.000 people, i.e. 0.146% of the population carries the infection. The total population of the USA is around 328 million. 95% of the USA land mass consists of rural area with a total population of around 60 million (~20%), the other 80% of the population lives in metropolitan areas (source: Wikipedia). If the infection rate of Seattle is used as a guide for the infection rate for the entire metropolitan population in the USA there are about 390.000 infected people in the country at the moment. While it is unlikely that this infection rate goes for the entire metropolitan population it is not out of the question given the high mobility of people in the USA. Even if actual the infection rate is a tenth of that in Seattle there are still around 38.000 infected people in the country. Who is being protected against whom by this travel ban? [1] https://www.youtube.com/watch?v=IzXQ6Bu9JVI https://www.youtube.com/watch?v=IzXQ6Bu9JVI [2] https://www.cdc.gov/coronavirus/2019-ncov/cases-in-us.html https://www.cdc.gov/coronavirus/2019-ncov/cases-in-us.html