It's usually a correct assumption that if something is on the level and is inherently "good," transparency will be exist, regardless of any presupposed and/or assumed objections. Conversely, lack of transparency is a good indication the opposite exists, regardless of the excuse given for the lack of transparency.
No, wherever government is involved, transparency tends to be a struggle, whther were talking about tax cuts, administrations, senators, treaties, bills, whatever.
The more the US has to bow to anti trade forces like unions in particular industries to liberalize trade, the more complicated the trade deal becomes, the more oversight becomes needed, the harder it gets to attain the transparency that would exist if anti trade "nationalists" fought for sovereignty rather than against trade.
Now, like I said, you can be against aspects of NAFTA and still be for free markets i.e. not a socialist so long as you believe in free trade in principle rather than "fair" trade. Which are you?