isolationism hasn't ever made a great society in comparison to diplomacy. when japan was isolationist for those hundreds of years entropy slowly increased to the point where it broke up when truly introduced to the world around it. also they were completely behind on many technologies and cultures
i don't get why people think immigration done the proper way is a problem at all, especially considering that them just being here and having them make a life out of themselves absolutely benefits the economy. of course there are some undesirables who would just be a problem, but that's why they get filtered out (as they already are)
the immigration process is painfully long and rough as is--and that's currently forgetin working lol