I wonder what would happen, if you have an accident in Cuba
A Canadian got into a car accident, I believe someone was injured, and it became quite a complex situation despite the young man being there legally. I believe at one point he might have been jailed and he WAS held in the country until a determination was made. That sort of hassle is an inherent problem in most third world countries, not just Cuba.
Keep in mind, an American in Cuba is NOT breaking their laws by being there and, unless he/she spends money there, is not breaking American law. So the situation is substantially more complex than what you have posited.
I imagine that getting consular support in that situation might be an issue. Seems to me someone here on SN was in Cuba in a consular type position. If he's reading this, he could probably answer that question.