A war of 330 millions of indisciplined people with relatively low IQ, spoiled by liberal ideas, "me, me" attitude and fragmented by race and ethnics, against 1.4 billions disciplined, united, extremely high-IQ people with an equally modern army. Who will win is easy to see.
US is probably waiting until US develops a supply of rare earths and other supply chains to isolate China. China should in the mean time stock up on a hundred years supply of iron ore/steel and other metals needed to sustain an economy. Build vast steel warehouses in Inner Mongolia to store steel to last China decades of high growth.
Don't tie China's hands in helping Iran, the way China went along with tieing the hands of the Chinese in helping North Korea.
Also comparatively, Germany during the kriegsmarine had over 1200 submarines, mostly less than 1000 tons. China is about 20 times the population of Germany then. Meaning China can make 1000 SSKs for 2050 and not even blink. That is the vastness of China's economic power. Small Island UK had hundreds of warships in UK history. China can produce 1000 warships by 2050.
Don't be blinded by past mistakes of the USA.
US did not defend against Iran missile strike because US would have shown cards of defense to China.
US killed the general for Iran to missile strike Isreal, who hinted at Iran that nukes could be used to destroy Iran. That was the trap. US did not want a war with Iran. US wanted Iran nuked out of existence by the zionist regime. Iran hit US military bases instead. And the plan was thwarted.
US cannot keep up in an arms race, without cia bitcoins going to over 1M per bitcoin. US would go bankrupt.
China spends barely anything on military compared to the US.
Don't forget about the strategy of low cost, high volume attacks. The next war is gonna see that. You want to overwhelm your enemy with too many targets, each protected. And you want to be able to swarm your enemy with over abundance of drone attacks and missile attacks.