North Korea persists because China keeps it alive. If China joined the rest of the world in sanctions and a no trade policy NK would fold in a week. The USSR l

North Korea persists because China keeps it alive. If China joined the rest of the world in sanctions and a no trade policy NK would fold in a week. The USSR largely collapsed due to its economic isolation. It couldn't keep pace with the wests military industrial machine and because the west predominantly sanctioned the USSR they couldn't grow to compete. Regimes do not last in total economic isolation for long. They require someone to prop them up. Of course, getting the whole world to ban trade with China would be infeasible if for no other reason than China already has enough influence in nations around the world to override the will of Europe and North America. Most of Southeast Asia and Africa would still do business with China even under UN sanctions because they are under the influential heel of the CCP at this point. You can look at Russia today as an example of sanctions somewhat working - continued sanctions by the west against Putins governments atrocities have not overthrown him yet but they certainly sow seeds of discontent against him. Its why Russia is spending so much effort to meddle in western elections, they can see the writing on the wall that a strong and hostile west will eventually erode Putin and the Russian mafias ability to hold dictatorship over the country.