“Other countries would not pay us the massive premiums that they do for our technology”
I disagree. First of all, you assume that the innovation in other countries will be in the same category as the US. For instance, a Chinese version of Google. This will not be the case. Innovation in other countries will involve technologies not seen in the US, not different versions of US technology. If China develops a new fuel technology that is 500% more efficient, everyone wins. The Chinese become rich and buy more Google ads. The US will use the new Chinese technology to lower their own costs. The Chinese will have developed a new industry altogether, just like the US has done with the internet.
The army argument is also not as important as you make it out to be. Right now, does China or India adopt US-dictated economic policy due to the threat of invasion? Of course not. China and India react to foreign aid and trade agreements. Productivity is far more important than military strength. For that matter, how has the US benefited from trying to control other countries with force? You cannot possibly argue that the Iraq war has positive NPV.
It does not matter if the US will not have the strongest military in the future. Canada’s army is small compared to the US, but they are not under any kind of military threat.
Your argument about innovation is self defeating. Innovation is the development of new technologies - things that no one has thought of yet. However, you depict innovation as a struggle for control of a limited pool of current markets and resources. Future productivity increases will come from industries that are currently in their infancy, not ideas that have been becoming more and more obsolete over the past 50 years.