I believe Alexis de Tocqueville's observations were severely skewed by his search for evidence that the French Revolution was not in vain. A much more fun but also strangely filtered view of America was Jack Kerouac's book On the Road. Kerouac makes you think that all Americans enjoy life to the full.

If you are looking for liberal roots, there's also John Locke who, in justifying England's civil war, influenced Sam Adams and the New Englanders. They read Locke and started rebelling in the 1740s with the Land Bank Riots.