Indian here. I was in India when the newspapers were brimming with the news of how USA denied the technology to India. Ironically the desire in India grew exponentially when the technology was denied. Suddenly everyone from politicians, scientists, engineers, and even the street food vendors and Bollywood actors were interested in India developing cryogenic engine technology. Many of them couldn't pronounce cryogenic correctly. 99.99% of them didn't have a clue what it really was or what would it mean to their life if India were to develop cryogenic engines.
This psychological effect is extremely powerful. An Iranian friend told me once "I don't want Iran to have nuclear weapons in general. But if USA and Israel do not want Iran to have nuclear weapons, then I want Iran to have nuclear weapons." It's all about sticking it to the big bully, proving yourself. Suddenly it gives a point to the people to rally around.
And the resentment it causes when people realize that someone else is controlling them is so powerful and pervasive that I think it needs consideration in foreign policy design.
I am not saying go on handing over technologies to nations. But Americans vastly underestimate this type of resentment. The future potential cost of such resentment should be adequately considered while deciding what is in the best interest of USA. If you really have to do it, then at least launch adequate PR effort.