I would love to see you take this and short the SP500, really put your money where your mouth is. Value is relative, and relative to the rest of the world the US is going to fare quite well. So good luck to you!
I think you are misunderstanding what he said. He's saying you have never gotten better off by betting against the United States in the long run, not that now is the time to bet against the United States.
I read the sentence two time to get what he was saying. Figured it out based on his first part of the sentence.