Does normalizing relations mean it will be easier for Cubans to get to the US to seek asylum? And if they do, will they still have a fast track to citizenship? That might make it easier for someone of Cuban descent to be elected President. What happens when relatively well educated, hard working Cubans compete for jobs other hispanics now have? What about Caribbean islands that depend on tourist revenue from cruise ships? Isn't the US Senate supposed to have say over treaty situations?
I'd be amazed if the administration has even thought about implications of a quickly imposed policy.