system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is the USA able to have a naval base in cuba and why hasn't cuba tried taking the land back?
gpt
Well Timmy, a big reason is that the base at Guantanamo Bay is old.  Very old.  In fact, it's probably older than your great-grandpa!!  "Gitmo," as it's called, was built all the way back in 1897, during a small war that many people have forgotten about called "The Spainish-American War."  As a result of that war, Cuba became it's own country, and basically rented the US the land for the base.  There's a treaty , which is an agreement between countries, Timmy, signed in 1903 that says while the land is ultimately Cuba's, the US has jurisdiction and control.  What that means is that Cuba owns the land, but the US can say or do whatever they want there.

Now, why doesn't Cuba want it back?  That's a very good question.  Another treaty signed in 1934 says that the land can only go bck to Cuba if BOTH governments agree to it.  As a funny story, we actually pay a monthly rent on the place!!  In 1903 it wasvalued at $2000, and that's what we paid.  The amount has been adjusted for inflation, so we pay Cuba $4,085 a month.  But the REAL funny part is that, under their old leader Fidel Castro, the Cuban government has only cashed ONE of those checks!!

In reality, Cuba doesn't care.  They have their own problems to deal with, yanking 45 square miles of land back from the US, while being a public relations triumph, wouldn't give them much.  All the buildings and equipment are US property, so the US would take it all back.  And if Cuba tried to take it by force, that would be considered an act of war, and the US would start doin military things to them.  So they just leave it there.