The reasons they give consistently are these:
1)Health care costs. Expensive and difficult.
2) Rents and mortgages on flat wages.
3)Food quality and availability of fresh food every day. Many people don't like the taste, quality or style of coping with food in the USA. No one with flat wages can cope with Whole Foods prices.
4) Personal relationships. The majority of friends are on the internet and no one talks to anyone face-to-face anymore. This is bound to become worse due to the pandemic conditions. Aleination is already part of the rat race no relationships of importance trend.
5) Lack of family friendly employers.
6) Lack of traditions and lack of historical roots. A lot of people in the USA move constantly from state to state and city to city and it makes for rootless communities that are again alienated.
7) The racism is real. Many African American people don't like the stress of dealing with racism as a constant in their lives. Neither do the Latinos.
Bad politics. It depends on your politics.
9) Lack of speaking foreign languages. Many US citizens who prefer living abroad ae fluent in more than one world language and have a lot more flexibility because of it. Study foreign languages while in the US and it will pay off over time.
10) Religious reasons. Many religious institutions want to expand their outreach and they do it by missionary work outside of the 50 states.
Here are some videos of people who left and the reasons why:
Good advice on the regrets:
y deja que mi alma se- pierda en- tus riachuelos
para buscar la fuente que te robó de niño
y en un ímpetu loco te devolvió al sendero.