Will China become a superpower and supplant us during this century?
China's power will surely increase--unless China breaks apart. But I sincerely doubt that China will replace us as the dominant power.
Even if China is one of many great powers, we will remain the dominant power. One reason is that we will still retain the bulk of the world's free military power
Strategypage has a useful site (that link is dead but I did find it--in 2019!--on the Internet Wayback Machine) that provides a single numerical value for a nation's land power, including air power that can support ground forces. The numbers on this site demonstrate why I don't worry about China too much even should they match us in absolute power. In short, China can't escape the logic of our geographical advantage.
First, I ignore naval power. We have absolute naval dominance. China can't fight us over here. We would fight China over there. That's advantage one even before we look at land power.
Consider that China has a land value of 2,757. America has a land value of 10,000. That's close to 4:1 right now. So China has a way to go to match us. Granted, this doesn't mean we can invade China and occupy them. Our power would diminish with distance and occupation is manpower intensive. But on the periphery of China we could beat them in battle. Say Korea, Vietnam, Taiwan, or Hainan, as long as we have the time to deploy our forces from America to the campaign area close to China.
If we had to, we could manage to deploy decisive land power against China even with 18 of our active and reserve Army and Marine brigades/regiments remain committed to Iraq and Afghanistan. It would take some supreme effort but we do have over 80 combat brigades in our active and reserve components.
But this good picture is even before we discuss geography. We have Canada to our north, with 166 land power value, and Mexico to the south, with 130. Even if both were hostile and we wanted to allocate twice their power to hold them, we'd have 9,400 in land power to spare. But since they are friendly, our full land power is deployable overseas.
But what about Cuba and Venezuela? Won't they tie us down a bit? Well, add in 31 and 65, respectively, for China's side with these two. And then consider our ally Colombia's 435 (which surprises me , actually, as a rather high number). And remember that our naval power will keep Cuba and Venezuela in check.
So let's look at the Middle Kingdom and their geography. China's 2,757 looks like a lot. And it is. But start looking at their neighbors. First of all, for the sake of argument we won't count Russia in this since little of their 1,726 value is lined up against China, and Moscow is in no condition to go toe-to-toe against China below the nuclear threshold. If Russia ever goes sane and joins the West, we'll revise this assumption.
But starting with India, which has 2,290 in land power, we already have a major counter-weight to distract China. Sure, Pakistan can help Peking if they side with China, but Pakistan's 699 points still leave India as a major Chinese foe.
Then look at South Korea with 920. North Korea's 688 looks mean, but I think it is fragile. Still, it probably nullifies South Korea as a Chinese foe in the short run, at least. But if Seoul does manage to absorb North Korea one day, you'd have a potential unified Korea with 1,600. Which is why China doesn't want a unified Korea, of course.
Then there is Japan with 523. And Taiwan with 449. And Vietnam with 327. Add in Australia with 172 and Thailand with 156. Sure, Burma throws in 202 on China's side, but the anti-Chinese alliance is adding up faster.
China has a potential coalition of 4,346 land power points to face immediate neighbors totaling 4,837. And this leaves Russia out of the picture, though that would probably only add in 200 points or so (as a wild guess) in the Far East to face China. I've left out others, too, like Indonesia, New Zealand, and the Philippines, who don't add much either way right now.
Oh, and we've forgotten to add in American power. That would be 10,000 points, essentially free to be deployed worldwide without worrying about our homeland defense. We remain the off-shore balancer who can intervene in Asia to sway the balance of power decisively against China.
Which is why I don't lose sleep at night over China's rise in power and wouldn't change places with them. Oh, if China is able to focus their power on a localized area, like Taiwan, they can generate local superiority for a short time--perhaps long enough to win that battle--but if we are able to mobilize and deploy our power, we can beat China on any battlefield. And we'd likely have powerful local allies to help us. China is a threat to our interests even now, but only if they catch us off guard.
Remember that geography (and our completely dominant Navy) means our power is free to deploy worldwide while China is hemmed in by hostile or potentially hostile neighbors. It's the Expeditionary Kingdom versus the Trapped in the Middle Kingdom.