Liberty Square has never run away the concept, unfortunately. Of course there's the Haunted Mansion, but it's not exactly 1776 America themed. Hall of Presidents and Liberty Belle are all they have relating to the proper theme of the land but a steamboat doesn't even make sense as they weren't invented until the 1800's.
Having a Revolutionary War set land on the banks of Rivers of America with the Sailing Ship Colombia going by would be so nice. Fill in the rest of the land with a Paul Revere "Pony Express" style coaster, American Adventure from Epcot (or even better yet, the Hall of Independence from Liberty Street), a Pocahontas canoe ride, and a Headless Horseman dark ride. Obviously this is not what the general public wants, but it certainly would be a better fit for Disneyland than Star Wars.