Half of Cuba is in the US after decades of a selection process in which supporters of Castro stay and those that do not love Castro leave.
Unless there is a right of return, there is no anti-Castro Cuba to support.
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There are about 11 million people in Cuba, and about 1,200,000 Cubans in the US. Some came here for [political reasons, others for economic ones, and many more just to be with family. That is a lot less than half that are here.
Castro is exceptionally clever. He knows that successful rebellions in Cuba have always originated among dissatisfied young middle class men like him, from Oriente province, with support among the university students in Havana.
He allows these young men to escape. Within a year or two, those not eaten by sharks have knocked up some chick here in Miami and have car payments to make and will never threaten his rule again.
There is a right of return. Any Cuban that comes to the Us has a right to go back. The catch is that the Castro government takes away the work papers one needs to get a job, so those who return have to depend on themselves or others to feed and house them.
Every Cuban, including those to go to the US and return, has a right to medical care, dental care and eyeglasses for free.
They are treated lots better than Palestinians booted out of Israel.
The most prosperous Latin American nation on the planet, measured by Gross Per Capita income, is Puerto Rico. Almost half of all Puerto Ricans live in the US, and all but a quarter live in the US for a year or more. So one could argue that Communism on a tropical island is less of a reason to flee from said island than Capitalism.
Of course, it's a lot more complex than that.
Spain has the least visible poverty of any Hispanic nation I have visited. Miami has worse slums and more beggars than Madrid or Barcelona. Spain is a moderately Socialist Democratic Constitutional Monarchy affiliated with the EC.
Public transportation in Spain is awesome. Clean and fast, and not too expensive.