Where'd you get the idea we've demolished most of our forests?
We have lots of forest in the NW states and Alaska, and plenty of forest in the Appalachians. Oh, and lots of forest in the panhandle of FL where many of our paper mills are located.
And we exploit those forests. But, a big BUT, we also replenish them so that they are self-sustaining. In fact I've heard it said that the forestry people plant more new trees than trees that are cut down.
And that, buddy, is not what Brazil is doing. So those oxygen producing trees of the Amazon are gone forever with no replenishment because of greed.