To what extent have Americans living during the last century remained true to their Revolutionary heritage?

Really, almost not at all.

Not at all. Most Americans are ignorant of their history/heritage, thus forums like this have to fill in the gaps.

Also the ideals of the American Revolution were destroyed by the American Civil War, the philosophy of a British Merchantile System of Alexander Hamilton/Henry Clay/Abe Lincoln, and finally in 1913 when the elections of Senators were changed from state legislatures to the people.