I think the reason the Cuba embargo lasts is because there was a great deal of money lost by the "rich and powerful" in the US when Castro came to power and nationalized all the businesses. Then there are the "refugees" in Miami that also lost what they had and want it back. To my thinking, not unlike the Palestinians in their fervor.
The families of both sets have long memories. This really wasn't the case within the US with the Chinese and Russian revolutions. An additional factor, Cuba seems to have little to offer but cigars and cheap vacations. China is a huge economy and Russia has oil. As in all things, Follow the money.