I'll let John answer that part, but, yes, NAFTA was to protect foreign investors in Canada and Canadian investors in the other two countries.
In the case of AbitibiBowater, they were legally established in another NAFTA country and therefore had access to the dispute settlement under NAFTA, including chapter 11. I'm uncertain about the history of the ownership of the company, and maybe John can provide more detail, but a Canadian and an American firm merged into AbitibiBowater, Abitibi being the original Canadian company and Bowater being the American.