What period of time? The nuclear age? Integration? Vietnam?
The Reagan years were still a great time to be an American... fall of the USSR. Even the Clinton years weren’t that bad.
My vote is Sept 11, 2001. Everything seemed to start on the wrong path after that. Lot of bad decisions made, seemingly out of emotion, but in hind sight, probably pre planned. The 2008 economic collapse put it into hyperdrive. 2016, was the best chance we had to turn it around. Looks like that chance is slipping away quickly now. Personally, I don’t see us lasting 4 years of a Biden administration.
Foreign policy will return to servicing global interests with no concern for American sovereignty or exceptionalism.
Reliance on foreign energy, surpassed in military strength by China and Russia, open borders and industry killing regulation and taxation.