Slop.

They weren't even using that land that often

Because you genocided the majority of them, you dumbfuck. Turns out when you kill over 90% of a population, it leaves a bunch of empty space.

But okay, let's give this whiteboy the benefit of the doubt (we shouldn't). Let's say the majority of Native Americans weren't murdered systemically by settlers. The reason the land in North America was the way it was is because it's the type of cultivation that makes sense for the environment it existed in.

No mules, cows, oxen, horses, etc. meant all farming was done by humans. And why go through the effort of plowing fields when you can just plant crops that can be left alone for the year? That way, you can just move to another area where crops you planted previously are done growing. You just rotate between areas, constantly collecting fresh food. This creates a wide abundance of food for a healthy diet.

Now along comes Whitey and his dumbass cuts down all these crops. He plants things that don't grow in their place, then doesn't rotate what he plants, draining the soil of nutrients. His solution to this problem isn't to change the way he grows food, Whitey's solution is to tear out indigenous foods and turn everything into cattle ranches. This isn't anywhere near as efficient as what the locals had been doing for thousands of years before Whitey showed up, but that's not going to stop him from calling them "savages" for not destroying the continent.