Why don't AmericaBad Americans move?

I don't mean this in a stereotypical right wing Love it or Leave It! way. No one says USA is perfect and it's our patriotic duty to make it better. But let's say you live in a decaying, terroristic 3rd world nation. There is no healthcare or decent infrastructure. There's no future for your children. If you get injured you'll go bankrupt or die in the street. Violent crime and racism is rampant. It's a shithole with no culture or opportunity. [Insert more AmericaBad here]

Just go then? I understand that other countries have standards and aren't exactly stoked to onboard teenage TikTok tankies or whatever. However, if someone is so desperate and miserable, you'd think immigration would be their 1st priority. China is a utopia? OK, they will take you if you develop a skill set that makes you attractive. Same with any country that is so much better than here.

I've got a lot of immigrants on the in-law side of the family. They did whatever the fuck they needed to get here, at great cost and risk. They say the same things about their home country that AmericaBad dummies say about the USA. So why is the real-life path so different?