While I of course agree that more economic freedom would be a good thing, I don’t think it’s the case that other countries are considerably better in this respect than we are, or that their success is a result of greater economic freedom.
Of the countries ahead of the U.S. in terms of economic growth, most of them are simply in a “nowhere to go but up” situation (the top 10 are places like Libya, Mongolia, Afghanistan, etc.). Of our industrialized peers, the countries ahead of us are places like Russia, Norway, Australia, New Zealand, Israel, and Iceland. None of these are bastions of the free market; of the countries ahead of us, only Australia and New Zealand rank above the U.S. in the Index of Economic Freedom. Of course, in terms of size of government, both Australia and New Zealand have considerably larger welfare states, including fully socialized medicine.
I would diagnose the problem rather differently. The problem in the U.S. isn’t economic (we’re still pretty damn good on that front), but rather one of identity. As this thread indicates, the U.S. is suffering from a crisis of self-confidence.