First of all this shockwave is halarious. I watched it with friends on the opposite side of the isle and they liked it too so it must be "fair and balanced or whatever..."
http://atomfilms.shockwave.com/af/content/this_land_af
Then, I saw it on CNN tonight. At the end of the story they said that the producers (JibJab) had been issued a cease and desist for copyright violations.
While obviosly Guthrie, it is most certainly also a parody.