The restriction is meaningless. The dictator can no more pay for food with hard currency than he can start his own space program. Castro awaits the day when his apparatus of state terror will be underwritten by his avowed enemies. He also believes that trade will lead to lifting the tourism embargo. Then vacationing Americans can help keep his Stalinist regime afloat.
China is halfway around the globe.
We have historic ties to the island and are home to 1.5 million Cuban exiles. It's not that we don't care about human-rights violations in China, but communist brutality in our backyard is even more of an affront. Mao Tse-tung has been dead for 24 years. But Cuba is ruled by the same tyrant who was in power for most of the Cold War. During the missile crisis, Castro urged then Soviet leader Nikita Khrushchev to use nuclear weapons against the United States.