Bottom line is there will be perhaps 10s of thousands of Americans, Europeans, Asians, etc. assisting in containing the outbreak. If you take your suggestion literally, any American who goes to assist takes a one way trip out of America, never to return. Same with the Europeans, etc. and everyone they interact with when they return home. It's a logistical impossibility, IMO.
I'm not necessarily opposed to much more screening and the rest, but those are difficult decisions.