I suggest you read Sun Tzu’s The Art Of War as well as the History of the Roman Empire.

This isn’t about China or the US specifically, it’s simply a mix of strategical thinking (nullifying an adversary’s main advantage makes victory far more likely) and how nations at the specific stage of a nation’s growth that the US and China are at spend money in their military - China is a large nation climbing towards Empire stage so their resources are increasing but they’ll still parsimonious in their use (because that’s exactly how nations climb up from poverty) hence it makes sense that as they have more resources to increase their military might they’ll put a lot of them in things that give them the most bang for the buck (and that includes countering their main adversary’s most relied-upon military strategy after the Vietnam war - the Carrier Group), whilst the US is at the late stage of Empire and already in decay, which means a fat, glutonous system of power used to lots and lots of wealth floating around and prone to grandiose projects both for the seeming prestige and because they’re massive patronage operations and opportunities for corruption and taking a slice of the money sloshing around, and said waste in their military is allowed to happen because, due to their past successes and their size, they trully believe they’re unbeatable.

This shit happens again and again in History - it’s not even the exception, it’s the rule: great empires get killed by the very elites in them becoming ever worse parasites and overconfidence in their might.

Things like the rise of a “Make America Great Again” movement spearheaded by a populist who himself is the ultimate rentier parasite is actually a pretty typical phenomenon of such a phase - again just go read the History of the Roman Empire.

The US became a military industrial complex state built upon military keynseianism during WW2. This worked well for them because of their unique advantages in the war, specifically being able to stay relatively disengaged while Europe burned, whilst also making immense profits selling weapons to the allies.

Essentially all of the European spoils of colonialism, the Atlantic slave trade and other economies of dispossession that made Europe rich went to the US as Europe self destructed. It was not unexpected either, the destruction of cultures, societies and peoples with a worldview of white supremacy was bound to bite back at them at some point (all conservative/purity politics eventually do).

There was also a massive brain drain with scientists escaping to the US for safety.

The US has managed to leverage that with 75 years of prominence as the global hegimon (some will argue it only became unipolar with the fall of the USSR) but that was never going to last forever. I wouldn’t underestimate China. America, like all empires, has slowly become fat and lazy. China is hungry to reestablish itself.

Now, the US and NATO makes up up 80% of global military expenditure so they aren’t going to just fade away but I would look at the US’ massive bet on AGI as a negative sign. If they accomplish it then, good for them, that’s probably another 50 to 100 years of US dominace but the approach reeks of desperation. China has had a much more measured and pragmatic approach to AI. If the bubble pops and the US takes too long to pick up the pieces, China will race ahead. China is already ahead on AI implementation in robotics which will have important military applications in the future as well.