If experience is exercise, name a more exercised force than the US military.
Our military is exercised to an extant, but it's also been exercising for fighting asymmetric warfare, and irregular combat, not conventional combat on a battlefield against a comparable enemy. It's like running 3 miles every day in preparation for a marathon, it's something and helps you work out some things, but its going to be very different once the gun fires to start the race.
How do you compare the exercise in Vietnam vs the exercise in Afghanistan? Is there a ratio of how badly beaten they are by people shooting back in flip-flops with soviet era AKs?
And not China either, because no matter how unexperienced the US Army is, the Chinese have virtually no experience other than trading shots and fist fights on the Indian border or acting like a school bully in their neighborhood - and most Chinese stuff is based on old Soviet shit (whose "quality" is currently being shown in Ukraine) or stolen Western tech.
Both sides in Ukraine rely heavily on Soviet equipment. One of the major problems Russia faces in Ukraine is the highly effective air defense infrastructure the Soviet Union built.
As for China, it has a mixture of heavily upgraded Soviet equipment (e.g., Flankers with modern sensors, electronics and missiles), and its own indigenous designs (for example, it's the only country other than the US to develop and produce a 5th Generation fighter jet). Given China's proven ability to develop high-tech products and manufacture at scale, why would you doubt that it's capable of producing modern military hardware?
Oh, they are certainly capable - but unlike the US, nothing what the Chinese build in terms of heavy equipment has been tested in an actual battle, neither has the logistics of their army or the command structure, both of which Russia sorely lacks in Ukraine. In contrast, the US has all three aspects nailed and refined for decades.
Also... who says that it's not all just a paper tiger? Everyone was scared about the T-14 Armata or a lot of other Russian stuff that was in reality just fraud everywhere along the chain. China suffers just the same problems with endemic corruption and a yes-men attitude as Russia does.
The US has plenty of experience, but it's all in fighting opponents who can barely fire back. No one has any idea how the US would fare against a real opponent. Even the shock to the public, which is used to relatively low-casualty colonial wars, would be difficult to gauge.
> China suffers just the same problems with endemic corruption and a yes-men attitude as Russia does.
I don't know if there's much similarity between the China and Russia, given that I only know the culture of one of those countries relatively well. What I will say is that based on my own observations, China is highly competent at pulling off large and complex projects - much more so than the US.