I don't understand how exactly he shaped America?
During the "Walden" period he lived simple, frugal life and invested his time into things he cared about (eg., measuring the depth of the Walden pond in winter). After his crops were ready for the harvest, he took them to the city and sold them with minimal effort, being fascinated by the fact that he didn't have to do almost anything, while he enjoyed all the luxuries of sensible, spiritual life.
He wasn't only author that did such things, but the society really never cared or cares.
Thoreau is forgotten, but for me, at least during his Walden period - he was a proper "hacker".
I'm quite sure that he would condemn the mark of being one of these who shaped the America (or world), because this is not what he wanted.