My opinion is that this is selective, based on factors like what the symbols represent, the extent of the offense, and how easily it would be to remove it.
Claiming that people who object to, say, the Confederate flag being flown on government property, are part of a crusade to rid all "triggering historical references" is a straw man argument. There might be people out there who have this as an agenda, but I doubt that many people subscribe.
In other words, objecting to a state flying the confederate flag, or some other flag that bears its likeness, does not automatically impute upon the objector an obligation to object to all things situated roughly similarly that reference slavery, and the objector would not be a hypocrite if he/she did not. There are people who are morally against zoos, for example, but who are not also members of PETA. Nor, necessarily, should they be.
2. The US is fundamentally different from most other countries because we have no "people" that define us. We have a system, and that system is predicated on our governing principles, which in turn are predicated upon a set of values. The extent to which these values are unique/important/great/distinguishable from those of other nations is subject to ongoing debate but they nevertheless exist and they are cornerstones of American mythos. Our "people" are just whomever was born here and those who move here who agree to abide by and preserve these fundamental values. On the other hand, the French will always be French. The British always British. Russians always Russian, regards of whether they have a Tsar, a Soviet Union, or a Vladimir Putin. Thus, most of the historical embarrassments of these nations can be chalked up to the foibles of Man. And since Man is imperfect, there will be the occasional foibles and embarrassments. Those transgressions that breach these boundaries are subject to greater scrutiny (Holocaust deniers, for example), but the mental calculus is still fundamentally different. Germans, for examples, can experience their own form of guilt for having given rise to the Third Reich, but they need not simultaneously apologize for being German. In Europe and elsewhere, the governments may change, but the people are always there.
To be an American, though, is to be a part of a particular system of values. When those values get betrayed or ignored by the powers-that-be, this cuts directly to our self-identity, because there is no such a thing as America without the form of government, the Bill of Rights and the other ideologies that go into it.
So, we will always be more sensitive about such matters as described above than people from other nations, and rightly so.