Bad decisions by the leaders of a strong nation weaken it massively, leading to a future downfall. History of great nations of the past shows this.
Read the history of the East Roman Empire, aka Byzantium. That nation had two falls. The first occurred circa the years 560-630 after Justinian bankrupted the Empire with endless wars. The East Roman empire was weakened by the debts, had a short reprieve but was further weakened in another war, then proceeded to lose huge swaths of territory to the Arab invaders in the east and Slav invaders in the west as its poor leaders and weakened army lost battle after battle against enemies it could have easily crushed in its heydays.
The second occurred in circa 1025-1072. The successors of Basil II reversed his decisions that aided the common farmer and small landholders. The aristocracy was permitted to gobble up huge swathes of land and reduced the people to serfdom. Thus the backbone of a loyal army was gutted. The army then was forced to rely on mercenaries who were unreliable in key battles, including the disaster of Manzikert in 1072. Further civil strife led the Seljuk Turks to occupy the crucial territory of central Anatolia. After that, the Byzantine Empire was trying to survive with one arm - its Balkan territory. Without the diversity of two economic bases, the Byzantine Empire, which at the time was far advanced technologically and economically over any empire or nation within thousands of miles, was mortally weakened.
Third, consider the great nation of Poland. In the 17th century, Poland was one of the largest and most powerful nations in Europe. Its aristocracy destroyed its unity in their greed for more power and land. Poland began a one way path to oblivion and partition.
What about America?
We have a huge debt still increasing; the money is being wasted and not spent on national improvements. We are being weakened by endless wars in parts of the world mostly irrelevant to American interests. The billionaires, CEOs and government bureacrats and thier allies grab more and more while the living standards of the common people are stagnant, National "leaders" bicker and fight for their own power while ignoring the needs of the common people.
Our only hope: the people will choose wisely ... soon. We need true leadership, a 21st century Teddy Roosevelt who will give the common man and woman a square deal, beat back the power of the Ruling Classes and their Pharisee allies, and stop fighting pointless wars that only enrich the military-industrial complex.