I think globally it is underreported because 40-60% of infections are asymptomatic. So everyone is underreporting, esp. in US where they are sending home-test kits that doesn't count into official figures.
Now, how much is it underreported in China compared to US, we don't know until we look at excess death rates which can tell us how much it is underreported.
I have a strong suspicion that even taking into account underreporting, China comes out FAR ahead of US because universal mask, contact tracing, mass vaccination, mass testing, robust lockdowns, no overwhelmed hospitals, strict international visitor quarantine and testing, lack of politicization of pandemic, and lack of misinformation.