While the TPP "IP" provisions might be banal, mirroring current USA law, the problem with the TPP is that its for all intents and purposes, a treaty. The citizens of the USA can't up and decide that allowing DRM circumvention is a good idea and we should now allow it: that would break international law. The citizens of the USA can't decide to shorten copyright length for fast-moving areas (computer science) because that would break international law.
The TPP enshrines poorly chosen implementations, just as the Berne Convention has enshrined poorly chosen implementations.
Do we care? Didn't legalizing marijuana in Washington violate international drug treaties that the US is signed to? It seems to be legal anyway.
Ultimately, laws require money to enforce and after people forget about the laws they find other uses for the money. International law is especially fuzzy in that it's not like there are judges, a court, and a jail for violators. If two countries violate each others' treaties, all they can do is penalize each other somewhere else, or start blowing each other up. Is someone going to bomb one of the three nuclear triad nations over enforcing copyright law? Probably not. So there is no international law that applies to the US, Russia, or China.
I live in Colorado, so you can't fool me with the "marijuana is legalized" thing. The Feds still regard marijuana as something that only Satan himself would touch, so marijuana businesses can't officially use banks, and there's a lot of other fallout. You certainly can't transport it very far. State line crossings are a big, big deal. About the best you can say is, "it's less illegal".
The US only ducks out on treaties that require it to spend less on military/defence stuff, in all reality. Unfortunately, really, really draconian copyright laws align pretty nicely with deep state issues: you have to inspect packets to decide whether a stream of bytes violates some "IP" or other, which gives a damn good excuse to penalize encryption, and allow even less oversight on search and seizure. Also, let's face it, it's really really easy to violate copyright even if none of us really minds. Draconian copyright gives yet another law to selectively apply to someone you don't like, who exhibits contempt of cop, or whatever. If the US accepts the TPP, all of the excuses will be "we can't break International Law" or "We'd loose out in trading negotiations" or "what can we do our hands are tied by treaty" for any modification of copyright law whatsoever.
The TPP enshrines poorly chosen implementations, just as the Berne Convention has enshrined poorly chosen implementations.