AFAIK, they're not limiting imports.
They are heavily embargoed since 1960s, which also affects other countries' abilities to trade with them, under the threat of themselves being sanctioned.
Canada and the EU trade fine with Cuba. Spain alone accounts for 20% of the trade.
In fact, both EU and Canada have regulations that prosecute any European and Canadian company that complies with foreign embargoes (Council Regulation (EC) No 2271/96 for Europe and Foreign Extraterritorial Measures Act for Canada).
Of course US can pull its gigantic economic and financial levers to out-out specific companies to choose "you either sell here, but don't sell in country X" like it has done with ASML, but it can only push so much.
You're right. But trade in US Dollars with other countries need to go through US banks, which can be subject to prohibitions, which can be done by political motivation.
Also, the issue of the PetroDollar complicates things internationally as well. US throws a tantrum when small countries (or countries it can bully) trade Oil in other currencies. That is very important to keep themselves relevant and with some control over international trades.
Yet another aspect is that if any goods, regardless of who is selling it, contains more than 10% of components, technology, produced by a US company, such seller requires an US Export license to trade such goods with Cuba.
I went to Cuba, and they were a good amount of Kia Picanto, Daewoo and cars from China brands I could not recognize. Of course they can't import from the US due to the embargo, and Europe would be unreliable for after-sell service.
They trade, limited by their own poverty, with countries that can't be easily bullied by the US.
Canada and the EU trade fine with Cuba. Spain alone accounts for 20% of the trade.
In fact, both EU and Canada have regulations that prosecute any European and Canadian company that complies with foreign embargoes (Council Regulation (EC) No 2271/96 for Europe and Foreign Extraterritorial Measures Act for Canada).
Of course US can pull its gigantic economic and financial levers to out-out specific companies to choose "you either sell here, but don't sell in country X" like it has done with ASML, but it can only push so much.
US laws apply to US citizens and companies.