First, America is NOT an Empire. We don't have an emperor but an elected President every 4 years. Not only is America very young, but it is evolutionary, a mix of all cultures with the best of the best from around the world. LONG before we "collapse" or evolve to the next level we will: Cure cancer and other diseases, use AI and quantum computers to solve many issues, improve Democracy and Education, colonize Mars, become completely sustainable with green cities, perfect our Justice system, make money less necessary for quality of life and develop defenses that can neutralize nuclear weapons far beyond shooting them down. Other countries will simply evolve in the same direction. It's simpler and more peaceful than you make it but it takes time.
Your vision is lacking.