The Romantic movement is generally seen as a reaction against the emphasis on reason that was characteristic of the Enlightenment. Therefore, this was not a significant element of American Romanticism.
2. Prevents people from being free.
Both authors believe that society can often limit people's freedom by not allowing them to become themselves. Therefore, they both encourage self-reliance and independence.
3. To ask them to preserve the memorial.
The author is asking Time and Nature to spare the memorial, and not damage it, so that future generations will remember what happened during the Battle of Concord. This is obvious in the last stanza:
Spirit, that made those heroes dare,
To die, and leave their children free,
Bid Time and Nature gently spare
The shaft we raise to them and thee.