>Can vast regions in the USA and other countries be re-forested? Yes, if the willpower is there.
China and India already plant a lot of trees.
US can sit back relax and dedicate that space to more research centers and get ahead while China/India are busy squeezing their population and putting up large pieces of land for reforestation.
Not every country has to do it, not many in Europe will shell out for reforestation.
The carbon in atmosphere will have effect nomatter where the tree is.