I think many people here assume that the nation state concept has permanence.
Nation states, as we have them today, are a relatively new invention. Europe, the first continent to have nation states, didn't even complete the process until the 19th century.
A 100 years from now? Who knows. Multinational corporations and international trade treaties and the like might make nation states largely obsolete.
Even in my lifetime I've seen an immense change. I work with people all over the world. Sins of a Solar Empire, for instance, was a collaboration between Americans and Canadians that was pretty seamless. Stardock's other products include people who work together from countries as varied as Russia, Poland, UK, Brazil, South Africa, Italy, etc. all working together as a single team.
Nationalism is something of a generational issue. I feel a strong sense of "patriotism" for my country but is weakens over time as I come to realize that the ideas and people that matter to me occur across multiple borders. This already has happened in the United States. At one time, loyalty to individual states trumped loyalty to the union of states. In a century who knows how things may evolve.
That said, it is unlikely that any *government* will be as powerful as the federal government of the United States any time soon. People talk about China but China's a blip. It'll be a very long time before the government of China is a major power in the world. China is barely at the nation state level from a government point of view. A lot of money is being made there but the government has little ability to tax it at this point. If any country is likely to be run by corporations in 50 years, it's China, not the United States.
The US's debt as a % of its GDP is less than most European nations or Japan. It's all relative.
Technically speaking, the US is still currently on a relative ascension relative to the G7 average when one looks at economic and military might.
China, Japan, etc. are very very far behind economically and of course militarily they're not even on the charts.
All this hubris one way or the other about nation states is pretty baffling to me to be honest. Where one was born was a matter of random chance.