I find it intriguing that people somehow seems to know who's behind stuff. It's not exactly hard to hide all traces, so I find it hard to believe that a state would fail doing so.
The US is clearly the one to blame for WannaCry. If it wasn't for the NSA leaking and not reporting vurnerabilities this would probably never have happened.
Perfect operational security is insanely hard, especially once an organization grows beyond a few people.
Theorizing about the ways one might perfectly cover all traces of an attack is quite a bit different from executing an attack against a large organization, moving through their systems and networks to look for sensitive data, exfiltrating the data, and then repeating this process for dozens of targets, year after year, without ever being detected or ever leaving a trace of anything.
More intriguing to me is how some people here are trying to claim this isn't North Korea, where it has all the markings of past North Korean cyberattacks and consistent with published findings about their specific departments tasked with the goal of raising money for Kim's private fund.
My guess is that it's most likely just a kid somewhere who had some fun.
Considering the kill switch the person behind this clearly didn't have much experience, so I find it very very hard to belive that some other state than the US was involved in this.
The US is clearly the one to blame for WannaCry. If it wasn't for the NSA leaking and not reporting vurnerabilities this would probably never have happened.