Let's say the TPP passes early next year with the US in it and then Bernie gets elected. Realistically, what can he do to get us out of it?

As I understand, the TPP is basically a one-time deal. Once you're in, you're in. So let's say Obama passes it, it goes international, we vote next November, and Bernie wins. He won't actually get the title until early 2017. What can he do to get the US out of it. The only thing I can think of is basically saying "fuck you" to it and then backing out of it with the power of the military. Is any company going to try to fight that? No court would take the case, and no other country would try to defend them because it would mean fighting us. Is there really any other way around it?