Italians were the first to shut down their borders to China, yet look where they are now. It's true that travel bans don't work.
However, a bit part of why Italy got where it did is because 10,000 Northern Italians fled to other parts of the country and took the virus with them. That's the part that scares me about the US border. With their crap leadership, there are going to be a lot of Americans coming to Canada for a safe haven and making things worse for us.
As it stands it'll be difficult. We don't need to take care of Americans fleeing their country as well.