The only way I would return to the U.S. if I were Snowden, is if he first received a Presidential Pardon for any and all crimes he may have previously committed. It would have to be worded in a way that it does not just list specific crimes they have talked about charging him with, but that he is pardoned for everything he may have done.
"A wise man ... proportions his belief to the evidence."
— David Hume, An Enquiry Concerning Human Understanding, Section X, Part I.