That question doesn't matter because national sovereignty would prevent other countries from doing that even if they wanted to. It's not a program it's even possible to consider without some really elaborate treaties that many countries would reject.

At the core of it what you're basically arguing is that nations are unethical because what citizenship someone holds influences things like their access to health care, and the solution to that would probably look a lot like the EU but completely borderless world-wide (with no immigrations or customs departments?)

I think you know how people would react to that. It's a pointless 'gotcha' question