The biggest hint is the perfectly lined up timeline:
The last time Satoshi was involved in Bitcoin was around January 2011, Silkroad launched in February 2011. So if DPR was Satoshi, this would explain why Satoshi suddenly backed off from the Bitcoin development, he was too busy developing and running Silkroad!
This is the only thing that makes slightly sense. With everything else you are mistaken I guess.
Nothing points to nakamoto being American. Also I'm pretty sure that Ulbricht does not have the technical skills needed to invent and develop Bitcoin.
Ulbricht however once said that he is not the original founder of Silk Road but that someone handed it over to him. What might be true (although not very likely) is that nakamoto is the founder of silk road but handed it over to other people later.
The best evidence he could be American is the timing of his message posts, which suggests he lived in the US-EST time zone or near to it (this would include the west coast of South America). Someone in Europe, Africa, Asia or Australia would have to have very odd sleep habits to explain the post history. This isn't proof of course, but is probably one of the better clues we have to go on.
DPR is clearly not Satoshi, at any rate. Very different worldview, and Satoshi was much more capable and mature in multiple ways.