"United States should downsize the population by ending all immigration and creating incentives for having fewer kids."
North Korea is the one country I can think of that bans all immigration. I'm comparing them based on the immigration policy the OP was proposing.
If you're just talking about immigration policies, why would other...
And by the way, how do you plan to END ALL IMMIGRATION? Do you want the US to become the next North Korea? If the US bans immigration, their international soft power is gone. You can expect retaliation, and then you can be sure that the economy is fucked.
Umm... what? How do you get from not accepting more immigrants to North...