Guantanamo and ObamaCare, while unpalatable to many, are still basically in the range of “things required by the reality we live in to exist”. Getting rid of things that fall into that bucket is sort of like fighting gravity. It’s really hard to do to begin with, and even if you succeed, everything is going to go right back to there in the end anyways. The only real hope that you have is to find a betterlocal (or hopefully global) optimum to replace it with.
These were solutions that were found as the least-horrible compromise to a problem that had to be dealt with, by a panel of experts.
Most of the things that Trump wants, like his wall, are the dumbass desires of a single man, in opposition to basically everyone who knows anything. They serve no purpose, aren’t the product of any reasoning, and (if undertaken at all) probably won’t be executed with much care (because they’ll give him just enough budget to build the thing as they can possibly get away with, and the people building it will slack while doing so, because they’ll know that it’s all pointless labor anyways).
He can’t actually leave the Paris Accord, so if we get a Democratic president in 3 years, that’ll be quick to hook back up. (Though, if a Republican comes in, that will become a rather painful one where the person will probably recognize that we should be in it, but because of the beliefs of the electorate, he might need to continue backing out of the agreement. The Paris Accord doesn’t quite fall into the heading of “things required by the reality we live in to exist”, and things that a single man can fully control aren’t governed by that rule.)
Trump did cost us the TPP, and that’s probably never coming back. But we also never started it.
I think that he’s been prevented from taking us out of NAFTA by saner heads. That would be hard to get back, but (at least as of yet) it doesn’t seem to be at risk.
Tillerson has currently made the State Department into a mess, and that could take some time to correct. But I think that the issue was that he appointed someone to review and make changes, while he himself focused on being lead ambassador to the world and trying to babysit Trump, just to finally be called back in for a review when the person he’d left in charge still didn’t have a great plan, and ultimately didn’t have the power to make the changes that are needed, because it would need to be Tillerson, himself, that would have to go to Congress and commission the requisite legislation. And while that’s unfortunate, and has caused some of the better staff to leave, it’s worth remembering that overall the goal was to streamline the department, and success at that could set it up for better future gains, even if there’s a temporary loss at the moment. (With Trump as President, it may well be that there’s no temporary loss because of Tillerson anyways. Our diplomacy was going to be in ass-nowhereland no matter what.)
Overall, Trump hasn’t yet changed much. Yanking NAFTA may be the only big thing that he could do on his own that would be hard to repair in a reasonable amount of time. Most of the things he wants to do will probably be trivially easy to undo, if he ever even gets a chance to do them.