The new scenario emerging from Canadian government sources, including several MPs involved in planning discussions, is that 80% of the world will become infected and about 3% of us (higher in developing countries, lower in developed ones) will die. A vaccine will be developed and we will all have to take the shot, possibly each year, and that's just how this will go. There are too many sources for this new scenario to site, and most of them are unofficial, so I won't waste time pretending that this is some sort of official prognosis... but it is a convincing picture of how this will play out.
Let's assume the USA returns to business as usual and does not attempt more stringent containment procedures. How is it possible that other countries could stay free of coronavirus? It simply wouldn't be. There is too much travel for it to stay contained in one country that is content to simply have the disease and not really care how many people get infected, because it isn't worth the economic damage from a protracted shutdown to them.
Like, imagine that the virus is eliminated in the UK, but is just another thing you can get in the US at any time. There are just so many problematic equations involved in that. Same with Europe. I mean, if this definitively can't be contained worldwide, we'd simply be better off pouring billions more into a vaccine and gird ourselves for the incoming losses while it is being tested and eventually deployed.