The short list? In more or less order:
Bush unilaterally declared the Kyoto Treaty dead. (It was probably doomed, anyway, but rather than forming a team to analyze it and then using their findings to propose a replacement, he simply announced that he was walking away from it for no better reason than that his buddies in the oil industry did not like it.) So, he begins his term with an isolationist declaration. He did the right thing in a horribly bad way.
Between his inauguration and the WTC/Pentagon attack, Bush specifically announced that it was up to Israel and Palestine to work out their own problems and that he was not interested in mediating. Since the U.S. continued its aid to Israel with no strings (and, to be fair, continued to send a limited amount of relief to the Palestinians), he sent a message to the Middle East that he was not interested in their problems and that he was completely supportive of the policies of Sharon.
Following the WTC/Pentagon attacks, he began giving lip service to an interest in the Israeli/Palestinian conflict, but all of his pronouncements were couched in language condeming the Palestinians or favoring Israel, rather than seeking to tell both sides to work out the difficulties.
Bush declared that the U.S. would never again allow any other nation to “challenge” U.S. superiority and declared the right of first strike if we saw the need–a principle that the U.S. has never claimed before. (We did not disavow it during the Cold War, but we always couched it in the language of actual self-defense. Even when we provoked the War on Mexico, we gave them the opportunity to fire the first shot.)
Bush unilaterally withdrew from the International Criminal Court, claiming that he did not want U.S. military personnel subject to “foreign” laws if they happened to be accused of anti-humanitarian crimes during a mission. With the U.S. claims for the right to bring other war criminals to justice (a principle established by the U.S. at Nuremburg), Bush presented to the world a claim that the U.S. was above the law.
After the WTC/Pentagon attacks, Bush made several claims that anyone who did not support the U.S. obviously supported terrorism–and further declared the right to seek them out and “bring them to justice.” So first he declares that the U.S. is not bound by international justice, then claims that the U.S. can impose its own justice on whomever it chooses.
When pushing for the war on Iraq, U.S. spokespersons verbally agreed to the demands of France that 1441 could not be an automatic trigger for invasion. Following which, Bush began sending troops to Iraq in such force that it was clear that there would be an invasion, regardless. Then, when pushing for the second (failed) resolution, Bush declared that he could use 1441 to justify an invasion, despite the earlier (spoken, not written) comments and despite the fact that Blix and company had not filed their own final reports.
(And while the argument has been made that 1441 allowed the U.S. to “continue” the first Gulf War on the grounds that Hussein did not follow his agreements of the truce, that rings pretty hollow in the international community–more especially since the U.N. Charter does not allow of pre-emptive strikes that Bush had claimed as U.S. (and only U.S.) prerogatives.)
In building his “Coalition of the Willing,” there has been substantial speculation that the “willing” were simply not “willing” to see their current aid or trade relations severed. The coalition appears to have been assembled by coercion.
Now, each of these acts can be argued on their own merits. Certainly, proponents of some or all of these actions cast them in different lights. However, the cumulative effect of these actions (and several similar ones) was to portray to the international community that the U.S. was going to act without regard to anyone else.
Bush has established the U.S. as, if not a rogue state, at least an utterly unconnected state that has no desire to work with the rest of the world on any issue.