Much of what the Early Romantics were trying to do was to create an American identity. Consider that the colonists are coming out of the American Revolution with no true sense of who they are as a country. Think about what it would be like to live in Georgia with oppressive heat, large plantations and with a landscape VASTLY different to those of the northeast. Then consider a colonist living in Massachusetts, near Boston where most people are still devout Christians and on much smaller farms. There are town squares where people gather on a regular basis. Bostonians and Georgians have little to nothing in common except for the Revolution and their empassioned enthusiasm for something new they can start on their own.
Now, early Romantic authors and in particular Wadsworth Lonfellow worked very hard at creating a national identity. They toiled to make old folktales and myths that people could get behind as being their own heritage. They made sure the natural settings of these stories were American. Consider "Paul Revere" which is a poem that idealizes a national hero who embodies what Longfellow believes an American should be: heroic, brave, loyal to his countrymen. Then look at "The Blacksmith" your average, hardworking American who is a family man, prays on Sundays and enjoys knowing he has worked hard to keep his family together and healthy.
Romanticism idealized not only the natural setting as the previous poster pointed out but also the American and his or her values. Look closely at Longfellow's writings and you will see that his protagonists value hard work, freedom, discipline, loyalty, and a sense of community.