I'd seek compensation for whatever time you were formally employed by the startup. I'd also reach out to some of the other companies I'd passed up job opportunities with to see whether they're still willing to discuss working for them. Be open, and honest as to why you're getting back in-touch with them, and perhaps explain why you chose the US startup over their opportunity to completely clear that question-mark in their minds.

Your situation is frustrating, but there's plenty of opportunity for smart, motivated, talented people. To help with your frustration, try to flip the story in your mind. This company is going to have to find a way to succeed without your knowledge, experience, and help. That's their problem now.

Good luck to you.