If you want to know which nations will be dominant fifty or a hundred years in the future, focus on long-term economic strength, not current military strength. The average person in China is still desperately poor, yes. And their military is no match for the United States military, yes. But the Chinese government has set it self up to be the economic 500-pound gorilla of the 21st century, and there’s little reason to believe that any other nation will be strong enough to compete with them.
First, the military imbalance does not matter. China’s military is big enough that no one is going to fuck with them. People can count the individual ICBMs and nuclear warheads all they want, but the fundamental fact is that China is well enough armed to inflict severe damage on all potential enemies. They’re back to mutually assured destruction with regard to both India and the USA; hence the Chinese need not fear any military threats from either country.
Second, the Chinese have bought up a huge pile of American debt. For as long as they hold this debt, America must pay them interest. In short, the Chinese are getting a lot of our money. Further, we depend on them to continue holding the treasury securities they have and buying new ones. If they suddenly dumped all those bills, notes, and bonds onto the market, the American economy would collapse. As long as they have this axe poised over America’s head, America has a weak hand in negotiating with them.
Third, they export huge amounts of crap and import relatively little. Countries that export will grow strong, as those that rely heavily on imports will grow weak. It’s a fundamental fact of modern economic history.
(As far as China being forced to import food, I don’t think that will have a big effect. England has been importing food since the start of the industrial era, but that didn’t stop them from dominating the 19th century. The important fact was that they were a net exporter.)