In all likelihood, the timing of the Khadr settlement was driven by deadlines agreed upon long before anyone knew NAFTA was going to be renegotiated. 
Even if that isn't the case and it could have dragged on longer, costing even more millions, it isn't the Liberals who have been ranting about it in the U.S. media.
It's Conservatives Rempel and Kent, cherry-picking the facts of the case, with the clear intent to create anti-Canada sentiment on the eve of the renegotiation. Americans and their media pay scant attention to Canada, but these two have done everything in their power to stir up animosity over this issue.
The Harper/Scheer/Kent/Rempel tag team was in power for most of the years since the firefight occurred, but only became so touchingly concerned about the widow Speers when they thought they could make political hay out of the issue.