There was a time when Vietnam was America's staunchest proxy war foe. This is not those times which explains why yesterday the president signed a landmark, controversial and not to mention hypocritical deal with Vietnam in which allows the U.S. to sell nuclear fuel and technology to its former foe, which will then be allowed to further enrich it. Why (because there is always a reason when the US does something so unexpected, and especially when nuclear power is involved)? Simple: as the Hill explains, the US "aims to help guarantee Vietnams' energy independence as China asserts a more prominent role in the region." Of course, the last time the US sought to prevent Vietnam's affiliation with a foreign superpower, the results were quite disastrous. One can only hope this time it's different.
Some more on why Vietnam is not Iran:
“I have determined that the performance of the Agreement will promote, and will not constitute an unreasonable risk to, the common defense and security,” Obama wrote in a memo for the secretaries of State and Energy.
And here is hypocrisy 101: "the deal aims to get Vietnam to import the fuel it needs for its reactors instead of producing it domestically. But it doesn't bar the country from conducting its own uranium enrichment, raising concerns about nuclear proliferation."
In other words, what the US allows Vietnam to do, just because it serves its own set of interests of Chinese sphere of influence containment, it will not allow Iran to do, just because Israel is still on the fences about whether the intentions of its latest weapons client are pure. "The agreement is also seen as a potential complicating factor in the ongoing nuclear talks with Iran. Iran has repeatedly accused nuclear powers, and the United States in particular, of a double standard in terms of which nations are allowed to run nuclear programs that are allegedly for civilian purposes only."
Then again, all is fair in Realpolitik, as the world return to a multi-polar theater, and in which the US is increasingly losing its superpower relevance.