You are being distracted by irrelevancies if you think this was the main issue. And probably quite foolish if you think democracy means 100% of people give their input to 100% of decisions.
The only thing that could improve this situation is that deals should be formed in complete secrecy, with no input from Congress or the Senate and should be ratified solely by the President via a treaty process.
You really want to ensure the Great Unwashed and those incompetents they elect indirectly don't get any where near trade deals, otherwise they might possible make "improvements" such as forcing through openness, accountability, fairness and equality! All of which are totally the anathema of good backroom deals.
It's a pretty seminal work, I'd encourage reading it.
(8000+ citations, https://scholar.google.com.au/citations?view_op=view_citatio... )
http://dfat.gov.au/trade/agreements/tpp/official-documents/D...
You don't want to show your cards in a negotiation, right? So how could the President and Congress say to the American people "this is what we're going to offer and accept from China" and pretend that the Chinese aren't going to hear it too?
Secrecy is often a horrible idea but this is a really complicated issue.