So the wood Americans used to build their frigates was somehow stronger than could be found in the rest of the world? And cannonballs just bounced off them? How big of an advantage did the Americans actually have because of their stronger hulls?
So, first off, it's not at all clear that British balls bounced off the hull of the Constitution, and it's certainly not likely at all that they would have done so if pointed directly at the hull. The source of the "Old Ironsides" nickname is dubious at best, and it's worth pointing out that Constitution was badly damaged in the battle with HMS Guerriere that gives us that legend (Hull returned to Boston for repairs rather than continuing his cruise).
Now with that all said, it's worth pointing out that Constitution and its sisters President and United States were explicitly built to be large, heavily armed frigates -- the term "pocket battleship" gets thrown around to describe them, but they were built to be larger and more heavily armed than contemporary RN frigates.
Some posts of mine that might offer you some more information:
https://www.reddit.com/r/AskHistorians/comments/2709jm/how_would_a_britishhms_frigate_built_in_1715/
https://www.reddit.com/r/AskHistorians/comments/2fs8qr/how_much_more_advanced_was_a_british/
Let me know if you have any follow ups. I'm feeling under the weather with a bad cold, but can try to get to them in the next few days.