http://en.wikipedia.org/wiki/Little_Ice_Age#Causes
there's a lot more to it than what you are saying. much more likely that celestial changes such as the muarunder minimum, volcanism, and changes to ocean salinity from the preceding warm period had something to do with it. i like the later theory because it shows a negative feedback loop, which is common in nature. you present a novel theory as fact and contort timelines in order to get it to work. sure, america was reforested after most all the natives died. but they died in the early 16th century, and america was largely reforested of its previous indigenous agricultural lands by the late 17th, which was the end of the little ice age.