That's easy: quantitatively. Consider how many F-35s America produces each year vs. how many J-20s China produces, to take one example. China absolutely needs to expand its nuclear arsenal by an order of magnitude in a few years, that alone is going to take a significant amount of money.You are getting way too fixated on a number. Instead look at what is actually happening on the ground and tell me where China is not closing the gap to the US militarily or even pulling ahead.
I don't advise that defense spending be doubled in a single year or anything like that - yes, all that would accomplish is an inflationary shock. However, that doesn't mean the budget can't be increased over a longer period (5+ years) under careful supervision to ensure that the money goes where it should.As a counter example, look at Ukraine and the ridiculous waste happening when you just blindly throw mountains of money at a problem and actually expect that money to magic armies out of thin air overnight. The real world doesn’t work like that.
That argument might have been decisive when Chinese growth rates were at double digits and China's technology was backward enough that all it needed was R&D. If you're developing a jet engine and need to test it for 10,000 hours, you can't build 5 prototypes and test each for 2,000 hours, so more money doesn't get more results because the limiting factor there is time. However, China has reached a technological level where it needs to pump out mass, and that is directly proportional to how much money is spent; more money = more J-20s.And that’s pretty much as fast as something as vast as the PLA can growth without wasting too much.
Furthermore, China's growth has modulated from its ludicrously high levels in prior decades. To be sure, it's going to be several times higher than growth in the West for many decades to come, but it's still not high enough that everything can be funded to maximal capacity without thinking about any compromises.
The people who look into that sort of thing estimate the "total" budget at 1.7% (down from 1.9%), so even taking everything under the sun remotely related to military spending, it's still below the 2% NATO minimum.And that’s just the official figure, if you don’t think China has significant defence spending squirrelled away under other budgets than I got a bridge in Africa to sell you.
If China put the phrase "Our intention is the conquest and subjugation of the United States and ending its existence as a political entity" in its constitution, it would be lucky to stay in the American news cycle for more than 24 hours. Nothing is going to distract Americans from fighting domestic political enemies, not China, not an asteroid hurtling toward Earth, nothing. America is terminally dysfunctional.If China put its actual defence spending in its white paper, it will absolutely cause the Americans to loose their shit and kick start a new Cold War and arms race. Why give them that clarify when a little ‘creative accounting’ on where certain projects gets their funding can help to keep the Americans complacent and more focused on fighting their ideological enemies at home?
The gain from increasing the defense budget far outweighs any galvanizing effect it might have on Americans. And hey, if I'm wrong and Americans do try to race China, let them. China will race them into the ground.