America has always been at its best when it lives up to its ideals, and at its worst when it discards those ideals. America has often been in the wrong, but on balance, the world has been better off for having a great champion of liberal democracy.
With Trump, it's not a question of believing things that are right or wrong. For the post-truth mindset, right and wrong don't matter. Democracy doesn't matter. There is only power. The second Trump presidency is the first time in modern history that America is no longer a great nation.