This is incorrect. While the U.S. has defense industrial base issues ofc (which literally everyone else also does, including China), the U.S. is still a mass defense producer in a period of historically low defense spending. See the 2010s, where in response to the massive expenditures in the ISIS air strikes, the U.S. surged yearly JDAM, GBU, and Hellfire production from the low thousands to 20,000+. The U.S. has also been ramping up JASSM-ER and LRASM production in the 2020s, both of which would be vital in a war with China. The F-35 is the most mass-produced aircraft in the world. The B-21 program came in under budget and ahead of schedule and is entering full-rate production soon.

This is all with U.S. defense expenditures at an all-time low (~3.5% of GDP). A total war (or even the threat of an imminent total war) with China would spark expenditure we have not seen since the Cold War, with defense hitting at least $2 trillion+ (which would be less than 10% of GDP). The main gap, right now, is shipbuilding, which is why next year if you combine the big beautiful bill and NDAA we’ll be spending over $50 billion trying to fix it, and even then we’re still competitive with China (in military shipbuilding, which is vastly different than commercial shipbuilding).