Not only were landscape paintings being produced in America, the world's frontier land, but the country's stable political system was realized by many (Americans, mostly) to have risen to such exemplary standards as to become a model for other countries to follow. During the 1848 revolutions in Europe, German American painter Emanuel Leutze thought to hearken back to the nation's "founding fathers" for inspiration and ideological clarity. He needed look no further than the nation's first president, George Washington, who had, during his presidency, almost instantly become a public hero and national icon. This well-known painting of Washington Crossing the Delaware, painted in 1851, demonstrated the epitome of the Romantic art style.
The nationalism of Delacroix's Liberty Leading the People is visible here. (The American flag is placed almost directly in the center of the painting). And Washington himself is given quite a noble image. Clad patriotically in red, white, blue, and gold, he looks onward fearlessly to the awaiting battle ahead. This painting is notoriously inaccurate historically, but what did we say about propaganda? This is not about the truth; this is about emotional reaction; this is about an idea. Here Washington is seen as a hero. There is perhaps much in this painting to compare to Jacques-Louis David's painting of Napoleon Crossing the Alps, but I would not necessarily call this propaganda (after Washington's political campaign had already ended half a century ago). The heroes which are made through propaganda are made as such in order to promote a cause, but Romanticism famously creates heroes merely for the sake of heroism (but I suppose you could argue that that's still a cause). And paintings like this were meant to inspire and remind us that, no matter under what banner or in what place, land or sea, heroes still exist, modeled after great men like this, who uphold those ideals that are universally and always right.