1. Can we avoid the cock-based rhetoric, please. It's really not OK.
2. I understand where you're coming from, and when I was younger, I used to feel this way. But let me offer a different perspective, one that isn't necessarily a challenge to your view point so much as a mollifying complement.
It's important for US presidents to maintain some continuity in foreign policy, for a number of reasons. When I say "continuity" I don't mean exactly the same; I mean that the policy should gradually change instead of radically swinging depending on the administration. And one reason for this is that we can't have effective foreign policy if other countries can't trust us to do what we say we are going to do, because the administration might change and everything gets dismantled. A substantial amount of foreign policy goes to treaties, agreements, protocols and the like.
Because of Trump, our credibility is almost shot. For instance, It was a calamity when Trump withdrew us from the Trans Pacific Partnership. That treaty was a dozen years in the making, and required the US to do a lot of cajoling of some of the included nations. It was no small ask for Malaysia or Singapore, for instance, to join a trade partnership that excluded Beijing. And yet with lots of diplomacy, they finally came on board . . . and then it vanished. Those countries gave China a small middle finger and for what end? I doubt they will ever trust the US again. It shouldn't really matter whether you think the TPP is good or bad; the point is that the sudden withdrawal was damaging to the United States long term, and that damage is considerably greater than whatever harms might have come from the treaty (editor's note: opposition to the treaty was rarely based in fact, because it was not what the far left and far right depicted it as).
And of course, what Trump did to the TPP, he also did to the Paris Accords and the Iranian nuclear treaty. And he could do to NATO. Or the UN. Or any other agreement, and then what will happen to our standing in the world?
I think sometimes people don't really understand what international cooperation does for us. For instance, the US has been able to cajole most offshore tax havens into policies that make it much harder for tax cheats and money launderers to stash new money there. We got Switzerland to open its banks to US law enforcement after decades of cajoling and diplomacy. It's not in Switzerland's interests to do so, but the US was able to use carrots and sticks to make progress on that front. Not just the US, but you get the point. Banking regulations are coordinated between international countries, and financial policy in particular. One of the reasons for the 2008 financial crisis is that Bush basically stopped caring about regulatory harmonization, and thus so did Europe, and thus the financial crisis was largely birthed out of a UK subsidiary of AIG that was following UK law but engaging in ridiculously risky practices.
So broadly speaking, our foreign policy needs to be predictable. It doesn't necessarily have to be fixed, but it can't be a thing where a new president takes office and does for foreign policy what s/he typically does for domestic policy. That's something to consider when evaluating Obama.
3. Now I understand that I'm talking about concerns that don't necessarily get to the heart of your complaint. After all, I take you not to be talking about the WTO but rather Allende and Mobutu, Saudi Arabia and Iraq. And those situations do present more of a challenge to the continuity I outlined above. The cost benefit is different. And where there's no real risk to America's reputation, quick shifts aren't as dangerous. There are still other reasons why continuity should be the norm, but let's stay with this one and analyze the Vietnam War. Would it have been a problem if Nixon had decreed in 1969, we were pulling out of Vietnam immediately? I don't think so. We didn't have war partners to speak of. Nobody except the SV kleptocrats wanted us there. The spectrum of world opinion there ranged from "you should get out" to "we don't give a fuck really," but nobody wanted us in.
Let's also take the second Iraq War. Bush 43 did assemble an international coalition, but other than the UK, I don't think anyone really wanted to participate. It was more of a "if you insist, we will grudgingly contribute." Some of the "assistance" offered by some allies was comically symbolic. There were countries, IIRC, that sent less than 10 soldiers as their "contribution." So if Kerry had won in 04 and stopped the Iraq War, nobody would have minded about the reversal (which is different from a decision as to whether a sudden reversal would have been a good idea on the merits, given that we broke it and thus had a responsibility to "fix it", which of course we didn't).
But on other issues, where our national interest more closely dovetails with those of our allies and thus our allies (and non-allies for that matter) rely on us, sharp deviations from policy are highly suboptimal. Yes, if you evaluate individual policies on their own merits, some of them were gross -- but that's not the same thing as saying we should just reverse them. In foreign relations as in law, sometimes consistency is more important than getting it right.
