The China travel ban was not quite that, there were exemptions and some 40,000 people entered the US after that time.
The European travel ban was way too late, hundred's thousand's of people came in to USA while european countries when being hit had.
The other big problem was there where no state border closures in the USA so people where travelling between states and spreading the virus. Had the closed borders many states would have had low rates of infections.
Imagine if we in Australia did not close off borders, we would be in a far worse situation but as it is the virus is mainly contained in Victoria. Few more in NSW and only small numbers in other states
