[hornokplease]

> I don't understand how exactly he shaped America?

From the link: "Thoreau’s love of nature and his advocacy of a simple life have had a large influence on modern conservation and environmentalist movements."

Beyond Walden, Thoreau's Resistance to Civil Government (also known by the title Civil Disobedience) has been cited as a major influence by civil rights leaders in the United States and abroad.

I don't think it'd be fair at all to say that Thoreau is forgotten in America, even if not everything about modern American life and culture conforms to what he might have wanted for the country.