I will list a few more issues with sustaining war of attrition by end of this decade for both sides. These are all hypothetical. And I think most likely very biased toward my personal view that a long war of attrition is not something American public would support.
China
food shortage - China currently imports large quantity of its food from Western countries and Brazil. If that's cut off, China will probably have to rely on Russia. Is the domestic production + imports from Russia going to be able to supply domestic needs?
energy shortage - If China's oil tanker/LNG imports get cut off, it will need to rely on land based solutions. They will have to import a lot from Russia
and Iran. It will probably have to limit personal oil usage by significantly raise oil prices so that everyday citizens rely on public transportation or EVs for moving around. Life style of average Chinese citizens will have to change a lot for them to have enough oil to last through a conflict. They will also probably work with Russia and Iran to get more pipelines added. They will probably have to continue to pay above market value to ensure they get the supply they need through the pipelines.
raw material shortage - This would be something that could shut down China's ability to manufacture additional weapons. US would have the ability to shut down China's access to minerals that are need for the produce new weapons. Although in some cases, China should still be able to import them from Russia or through Russia
Currency Collapse - I actually don't think this alone will cause China to lose, since during war time, they'd mostly rely on domestic supply chain and output. The only major issue here is with importing energy and food and other raw material from abroad.
Losing ability to fight - I actually think this is pretty hard to do or at least take a very long time. For it to happen any sooner, it would entail US for ability that we have no knowledge about. Just relying on cruise missile strikes along will not degrade Chinese military base or factory production to the point where they run out of aircraft and ships. It would take a long time to completely remove the threat of Chinese diesel submarines and land base anti-ship ballistic missiles. This is all assuming that USN is able to sink most of the Chinese surface fleet around first chain of island, which seems to be a tall order.
I think in order for US to actually be able to destroy the Chinese military industrial complex, something like B-21 would need to be able to enter Chinese air space completely undetected without escort, be able to stay undetected while dropping bombs and then fly out of the country undetected. That seems really hard to do given the amount anti-stealth technology they've invested in. I was listening to the ShiLao podcast and they basically said the Chinese anti-stealth radar had unexpectedly long detection range against F-22s. While the accuracy is not good enough for missiles, they are more than enough for guiding fighter jet for interception.
Unless B-21's stealth is a completely different level from F-22/35, it's hard to see how they could consistently make it through Chinese air defense. The other possibility would be US having some type of hypersonic missiles that's just not intercept able by Chinese air defense. The problem here is that such weapon is likely to be very expensive and produced in limited in quantities. I don't think they could be produced in such a quantity to keep Chinese military industrial complex off line sustained period of time.
for America.
energy shortage - It might sound crazy that America would have energy shortage, but it's entirely possible. Think of the scenario where America cuts off oil supply to China. The obvious move for China in such a scenario is to bomb the oil transport facilities so that America does not have access to oil either. More importantly, China would be able to use H-20s to bomb fuel depot in Japan and US military bases that would make it hard for for USN/USAF to sustain a forward operation.
supply chain disruption - It seems to me that this is a likely event since America uses a more global supply chain. At a minimum, China would be able to shut down all that chip production in Taiwan and all the. suppliers in Japan. And they'd be able to comfortable threaten Singapore and South Korea to not ship parts to America. If they are really threatened, they could resort to bombing that part of supply chain.
raw material shortage - This could become a huge issue for America too. Since Chinese owners operate a lot of the mines for metals used in weapon production, they could just destroy their mines or stop production at the start of the war. Or they can pay those countries to not sell to America. The latter option might not work if they have a currency crisis. The former should be able to stop production for months.
high inflation/currency collapse - In general, this can be considered as how willing are the American public to live significantly harder lives in order to stay in a war in another part of the world that otherwise does not affect their day to day life. Especially if we have an inflation crisis along with a currency crisis and stock market crash.
Losing the willingness to fight - I think the big question here is how much is America willing to tolerate in such a war? Are they willing to tolerate the loss of 1 or 2 super carriers? Are they willing to tolerate the loss of 4 or 5 super carriers? If they are not willing to tolerate the complete loss of one carrier, then that will limit how close they are willing to have the carriers to Taiwan. The closer they are, the more they are facing the danger of Chinese diesel sub threat and anti-ship ballistic missiles. The further they are out, the less effective the F-35s will be. And they are also likely to more quickly get worn out by PLAAF and leave their flight deck open to missile decks. While those missiles strikes most likely won't be able to sink the carriers, they could take losses on planes that are on the deck of in the hanger. Keep in mind that it takes many hours of maintenance for 5th gen aircraft to fly one mission.
If China has a significant advantage in the number of J-20s vs F-35Cs, they can easily wear out F-35C interception efforts and be at advantage against non-stealth aircraft and the rest of the escorts. Similarly, land based USAF F-35As would have similar issue of wearing out. Especially if China is able to take out the military fuel depots and communication stations. As we saw with Hurricane that passed through North Carolina a couple of years ago, USAF could not fly away their F-22s even when a hurricane was coming. As such, they suffered large amount of damage. The Japanese air fields closest to Taiwan are unlikely to have the same of air defense as Honshu. As such, it's not unreasonable to expect that after initial LACM strikes degrade air defense early warning systems, H-20s could come pretty close to these air bases without getting detected and keep these military bases out of action. The further USAF has to station its F-35s, the harder it would be for them to make real contribution. I think we also have to consider pilot fatigue in this type of scenario. It is very draining for pilots to fly 5 to 6 hours missions with heavy helmets. Aside from aircraft fatigue, pilot fatigue would be another issue that is not in USAF's favor in this scenario.
As such, I think there is a lot of factors here, but I don't see the reason why US would be excited to get in an all out war here once PLA gets strong enough. Russia is a big x-factor here. if they continue to supply farming goods, raw minerals and energy to China, it would mitigate a lot of the issues from having China's trade routes cut off. They could also potentially secretly permit China to allow Y-20Us refuel H-20 over Russian air space, fly through Arctic Ocean into Canada and launch LACMs into US military industrial complex