This won't do anything. The attacks are not from the offending countries they're from botnets of compromised devices.

North Korea doesn't care if you limit their internet they already allow people to go outside their own.

perfect, then we just nullroute at source with Flowspec, even if we change the goalposts a thousand times in this thread there does exist a technical solution to this problem.

Just not enough economic or political incentive to pay for it.

It's not changing the goalpost. You're just describing a solution that are heavy-handed, yet incredibly easy to circumvent.

America already limits its upstream to China and Russia through a private companies such as Cloudflare and Spamhaus. It's often the case that for Chinese users seeking to escape censorship, once they've worked their way through the Chinese Great Firewall, they find themselves in front of the American one.