It would be real tough to be out there "living off the land". North America is still full of remote corners but most are in regions that are inhospitable. Long term survival can be accomplishd by a resolute, trained and equipped individual if one is willing to compromise. Wild Bill Moreland is the model for this. He spent 10 years on the run in the wilderness of the Bitteroot Range along the Montana-Idaho border. He hunted, snared, fished and he also broke in to Forest Service lookout cabins and pilfered what he could. Point is that to live off the grid long term you have to use what is available. Be resourceful and not worry about "pure" survival or self imposed rules.