Yes, they come from Cuba because the US is the closest countries with opportunities, just like many people flee to Italy from the north of Africa or from the middle east. Also cuba is a bad example because of the https://en.wikipedia.org/wiki/Cuban_Adjustment_Act and https://en.wikipedia.org/wiki/Wet_feet,_dry_feet_policy. They are incentivezed to leave the totalitarian regime of Cuba (which is not socialist to be clear) to the US. The goal of bringing up Romania and El Salvador was to show how the bad conditions at the time forced people to leave. People don't leave countries that are doing well.

Also, your friends are probably from a select group of people who came in highly educated. People who come in with 0 education (like my parents) are not treated well in America. Many of the Romanian families that I grew up with in South Florida have gone back, as America honestly isn't that great compared to what has developed in Romania over time (its pretty nice now!).