The American idea has at its heart a fundamental contradiction: between patriotism, civic duty, the power of law, and the collective good on the one hand, and individualism, libertarianism, and free thought on the other. This contradiction is deeply ingrained in our national myths and rituals. We salute the flag and revere the Constitution, but we also admire the dangerously unconventional Thomas Paine and the smugglers and rioters at the Boston Tea Party. (One wonders what the proponents of the "Broken Windows" theory would have thought had they been there to witness that seminal act of public indecency.)
Neither end of the contemporary political spectrum escapes this contradiction. On the "left", we trust women to make choices about their own bodies, but distrust the free market; on the "right", we want to regulate marriage but not corporations. Both sides profess to encourage debate and discussion, yet both are susceptible to groupthink and echo chambers.
In mathematical logic, when a system contains a contradiction, all propositions become true. Perhaps the contradiction embodied in the American idea is what generates the messy diversity of opinion and behavior that, at its best, invigorates our society.
(The dig at the "Broken Windows" guys is in there because they contributed a lame essay to the original Atlantic issue that published famous people's essays on the "American idea".)