Old Ike started it all, and several have tried to lessen the embargo and Congress has refused both parties of guilty of continuing this nonsense, but then again the old fart running Cuba has never been easy to get along with or a very accommodating politician.
They bring very little to the table put heartburn and creating constant arguments about the embargo. China on the other hand with their military might, is a formidable force in the world today, both militarily and economically...where do you think most of the world oil supplies are going today?
China is, and will continue to be a world power that demands attention, cooperation and close scrutiny. Cuba either involved with trade in the US or not, is simply a pain in the ass and a risk to American politicians if the free Cubans decide not to vote for them because of a reduced stand against Castro.
The bottom line is not about economics, freedom or foreign affairs; it is about votes, even if the population of free Cuban voters is insufficient to swing anything but local Florida elections. Politicians when they attempt to understand and play politics are mostly stupid people.
Below is a site that will provide a little history of the embargo and the actors involved. Interesting reading.