While it may be difficult to quantify manufacturing output using a single metric, 4x industrial output sounds exaggerated to me. The most widely cited figures for global manufacturing, which measures industrial value add, puts China at just over 30% of the global total and the US at around 15%. During WW2, US had more than 5x the Japanese GDP and 10x the industrial output. US produced over 15x more steel, 10x more coal. Most importantly, the US produced the majority of the world's oil at the time, while Japan was critically hamstrung by lack of access to oil. I would argue that Japan's oil shortage in WW2 was a more significant limiting factor to Japan's warfighting and industrial capabilities than rare earths would be for the US today.
Sure, US has the capability to strike Chinese mainland, but not with enough ordnance to even put a dent in Chinese wartime production. Any fires that the US would be able to direct at the Chinese mainland would be prioritizing military targets.
I don't get why you are always advocating to war and destruction. You exhibit the same behavior in the Iran-Israel thread, calling for Iran to continue fighting regardless of the damage and destruction that would cause Iran. China doesn't want to fight the US. China's goal is to continue pursuing economic development and technological progress peacefully to the point where the US simply becomes irrelevant. I don't understand your obsessions with seeing a showdown between the two most powerful nations on earth. If war were to actually happen, you are aware of the fact that you, I, and just about everyone in the world will be in for a very bad time, aren't you?
China produces roughly 10-15 times more steel than the US, per year. That's where industry truly counts. Not just having a lot of businesses (which, in America, mostly just resell Chinese goods, anyway), not GDP that is inflated by higher costs and pricing, regardless of whether counting nominally or by PPP. But real, heavy, vast production and supply chains. Europe and the US think that if they have a large GDP, they can win wars, but you can't win a war just because your factory of Rolls-Royce cars pulls in more money than ten Chinese foundries that produce millions of tons of steel.
China's steel production is more than twice that of modern India, Japan, WW2 USA, WW2 USSR, and WW2 Nazi Germany combined, and the latter three countries were fully mobilized and operating at peak production during the greatest war in human history, while China is operating in peace-time. And steel is a massive factor in war.
Oil is too, but china has vast oil reserves, perhaps not as much as other oil-rich countries, but certainly sufficient, as well as a massive oil stockpile. Plus, any extra can be easily brought in from Iran, or even better, their close and absolutely oil-rich ally that conveniently borders their own country: Russia.
And of course we musn't forget population size. China's population outnumbers the US by more than four times, whereas the US had a population advantage of about two times relative to Japan in WW2. Then there's land size, which Japan was totally lacking in, whereas China enjoys a massive advantage in that regard, and that's without even factoring potential extra land usage granted by Russia.
China is already a monster all by itself, add Russia to the mix and you have the most powerful alliance in history. Of course I'm not implying for china to let it's guard down or grow complacent, but they truly are at a point where they would be practically unstoppable if they had to go toe-to-toe.