Don’t ask Donald Trump the above question. At the other end the left with its often correct exposes of rightist racism and ethnocentrism misses the point of the real crisis: we are not talking about a few million, we are talking on the order of a billion. A billion refugees? Even the left will shut up here, and I hope start thinking about a problem they might well inherit. Putting a billion people on welfare is not going to happen.
The open space in the US and Canada (and the Norway/Sweden zones) is still immense.
To answer the question, for what it is worth: if China can feed a billion plus people, and if it is to be a question of hundreds of million dying, the EU and the US/Canada could probably feed two billion: on their shores. I wouldn’t bet on its happening. what is going to happen? Is the climate prediction on the level?