The Chinese have nothing on the US.
If people make fun of them it's probably partly because of three reasons.
1) Japan is in denial they exist, to the point they have some rather elaborate schemes to diminish their public presence.
2) They're paper tigers, in other words they've not actually fought in a war since WW2 where they were still using some messed up choices in how to run things.
3) Your average anime/manga writer doesn't have the first inkling of what a modern military force is actually capable of, or how they do their business and just sees them an obstactle for the author's monster or superman to be a big serious dominating threat. If the mere mortals can handle the threat just fine, the whole saving the world plotline just doesn't work.
I seem to actually recall the US Navy's 7th Fleet getting slapped around more often the JSDF in Japanese works. Magic User's Club is one of the few ones that actually did a decent job with the concept.
China can probably nuke Japan, but they can't defeat the Japanese Navy and the Chinese don't have the projection power to land troops even if the Japanese NAvy wouldn't be splashing the craft attempting it. Doing an Amphibious Assault on Taiwan is questionable, Japan isn't happening.
I say can probably nuke because missiles actually lighting up and hitting what you want them to is never 100% even with the American ICBMs, Russian and Chinese ICBMs naturally have higher failure rates. Given the relatively small number of Chinese nukes there's no real gurantee that between the USN and the JSDF Maritime Fleet ballistic missile defense systems and the failure rate that anything would actually get through and go boom. It would however be suicidal for the Chinese to pull that kind of a stunt, which is why they realistically won't.
