The United States' withdrawal from Afghanistan doesn't mark the end of US power in the world, but it does mark the end of the neoconservative era. I don't see how that can seriously be doubted.
The neocon ideal was that the US was a virtuous power -- possibly one divinely ordained -- which had a moral duty to gain itself another century of global dominance and spread liberal democracy to be taken up instantly by the people it invaded.
That is utterly gone, a memory of a delusional period after the end of the cold war and before China was ready to assert itself on the world stage. It failed everywhere it was tried. But rather than admit the flawed nature of the idea, the last stragglers at History Airport are looking for something, anything, to blame.