The "most onerous portions of USA copyright law" are tiddlywinks compared to the "most onerous portions" of Japanese copyright law (citation Fuji vs. Jazz Camera, Lexmark vs. Arizona Cartridge Manufacturers). Unfortunately, Japan's interpretation of protecting OEM rights internationally ("e-waste" takeback laws were invented in Japan for reasons having NOTHING to do with environmental destiny and EVERYTHING to do with re-manufacture and reverse-engineering) seems to have metastasized in Asia. EFF is on the right side of this, but pulling TPP's finger from the hole in the dike may result in "the perfect is the enemy of the good", ie if the USA was the strongest proponent to protect copyright - Disney lobbyists aside - then it's speculation whether TPP "could have done more".
I'm not an expert in TPP, or what concessions USA made or even brought to the table to protect USA lobbyists. But I'm above average as expert in the fact that trade is generally anti-protectionism, and protectionism is generally anti-trade, and TPP, NAFTA, TAP, etc. are generally trying to remove barriers. Glad EFF is there, but when I interviewed them about Chinese and Japanese law they said they didn't have enough bandwidth to be experts in that, and since the point of TPP is to leverage Japan vs. China (which despite certain idiot comments is NOT PART OF TPP), we had to find common ground, ie try to compromise with Japan.