Bulgaria has free healthcare and university education. People in Bulgaria are also very unlikely to be killed by police or die in a mass shooting. Bulgaria also has less people incarcerated per capita than the US. Bulgarian workers get mandatory 20 day of PTO a year.

I could imagine lot of people who would think they are better off there than in the US.

E: There's of course a lot of things that aren't great about Bulgaria - it is probably the least developed and most corrupt EU country - but since US is very unequal, it depends whether your baseline is millionaire FAANG software engineer or minority person working in Walmart.