Empires are a lot like people.
They start out young, small and weak. They begin to learn, and as they learn, they grow larger.
Sometimes they lose a little power and come back. But eventually they hit their prime, using what they have learned.
Finally, they begin their real, permanent decline. They try to hold on to old things they knew, talk about the good old times.
But they don't regain their power. Instead they die. A new empire takes over based in another part of the world, with a different culture.
The reason is simple.
Empires don't form because a country 'deserves it".
No. Instead, the empire is created when one country invents/discovers something dramatic. The US empire is fairly obvious. A combination of capitalism and nuclear weapons made us a 'superpower'. Those have spread to other countries, but by then we were already a superpower.
The truth cause of our success is the spirit of freedom and innovation. Because you see, neither nuclear power nor capitalism were invented here. Europeans (mostly Germans) invented nuclear power, but came to America because of the lack of freedom in Europe (Nazi Germany). Adam Smith, a Scotsman, was the father of Capitalism.
The United States true power came from embracing progress and liberalism where other countries preferred conservative values. Note I am talking about real conservatism which is founded on the respect for tradition, not the new pseudo conservatism that embraces libertarianism in theory (though not in practice).
Because you see tradition is what kills empires. When you start valuing things because of how great they were once as opposed to trying to make things better, then you are going backwards as opposed to forwards.
You can never back into an empire, no matter how great the old empire used to be. Instead you have to charge forward into the unknown.
Any country that talks about how good the good old days were and how bad (immoral) the young folks are is doomed. They can never become strong and powerful because they are preventing new ideas from bringing new power to you.
You can't copy your old ways to get power because everyone else already knows your old secrets. You need new secrets, new ideas, you need liberalism.