The US sugar industrie is one of the most protected/subsidized ag industries in the world. US sugar prices are protected at levels well above world market. The US sugar industry is lorded over by the very rich, powerful and politically influential Fanjul Family. Even the US government is hesitant to mess with this family.
Are you suggesting that the price of cane and beets in the US is supported at such an artificially high level that it is economically not feasible to make ethanol out of cane or beets in the US? Well, if that's the case why not support ethanol production from cane in Cuba and buy ethanol from Cuba, and in exchange Cuba could buy the stuff we're good at making, video games and Kentucky Fried Chicken.
Cubas cane industry has been left to implode (around 04/05, they decided it would be better to grow rice). They tore down many mills and those left are in serious need of upgrades. Cubas main concern is to have enough molasses for their local Rum production. Little if any money or desire to build new milss and ethanol distilleries. Cuba is unable to meet its forward sales of raws to Europe from which it borrowed via COFACE. In fact Cuba is importing refined so that they can export as much of their raws as possible.