Cuba can’t pay because Cuba can’t conduct normal finances with the rest of world because of the US embargo
It’s like having having someone handcuff you, cuff you feet and pin you to the ground and rest their knee on your neck and ask you why you can’t get up on your own.
You are technically correct … but there are several convoluted rules and regulations controlled and mandated by the US that it makes it either very difficult or impossible for most countries to do business or trade with Cuba.
Cuba can trade with anyone they want … it’s just purposely made so difficult that very few do so and the ones who do provide very little in exchange.
What I read in your link is not so much Political fact but a disagreement of experts.
What I read in your text is that trade is to difficult, however it is done.
The question is, with what currency? The Cuban dollar is not really worth anything outside Cuba, so they can only rely on exports to fund currency needed to buy imports.
This is true, but not due to a US embargo. I should think that the state has access to many different currencies. But, in the end, they have limited resources. Cigars, some Rum (though a lot of countries distil and export rum in the Caribbean). They used to export mercenaries and doctors but noone is buying now.