The problem with this? No Indians. Any program that calls America a wilderness and then show plucky colonists "taming" and "civilizing" it is a falsification of history. It's the umpteenth example in a long line of pro-colonizing propaganda.
A clever person might respond, "Well, if they had included Indians, wouldn't you have criticized that too?" Answer: Yes, if they were stereotypical. But Peter's Progress could've included non-stereotypical Indians in the story's context.
How to fix Family Guy
Here's one way the creators could've done it. Every time a colonist uttered something such as "It's a wilderness," a chorus of authentic-looking Indians could've popped up and contradicted them. This could've been a quick 'n' easy running joke throughout the episode.
Colonist: "It's a wilderness." Indians: "No it's not."
Colonist: "Our beautiful home in our beautiful land." Indians: "Our home, our land."
Colonist: "And so everyone lived happily ever after." Indians: "No we didn't."
The Indians could say a lot more about the colonists' genocidal actions, but that probably wouldn't be funny. What would be funny is Peter's pushing them back into the bushes they came from. It would almost be like a game of Whack-a-Mole.
Incidentally, don't waste my time telling me Family Guy is just a TV show. I know that. I also know that every form of entertainment--from books to plays to movies to TV shows--has contributed to our national mythology. These ideas don't materialize out of thin air; they're conveyed from generation to generation through the media.
For more on the subject, see TV Shows Featuring Indians.
Below: The colonists discover a "wilderness."