Indeed, China is mostly a regional nuclear power. But we're talking long term here, and China is very aggressively modernising their military including their nuclear arsenal (which is estimated as about 100-200 warheads

"Very aggressively modernising" ... ? hehe :-) Would you characterize the US modernization of its stockpile as aggressive too? I mean, since china hold about 200 nuclear devices opposed to the US stockpile of 10,656 the US must be VERY aggressive (following your own, rather strange, logic)

"The article you linked to is by a organisation that has on it's agenda nuclear disarmament, which makes their estimates of Chinese nuclear forces about as reliable as Greenpeace's estimates of the effects of pollution"

You can't afford to be more specific, can you? What in more concrete words is so unreliable in this article you say?

(look how small China's nuclear forces are, the U.S. should start scrapping nukes immediately)

Do you really think that this [US] country can't afford to reduce its nuclear arsenal? Are you serious?

Also, a nuclear deterrent isn't always used against nuclear weapons, it works as a deterrent against a conventional invasion as well

What makes you think that? What kind of sane politician would use WMDs against another country if it invaded someone with conventional forces? Did your enormous nuclear arsenal scare Saddams armies off from Kuwait in '91? No. Did you use nukes agains saddam? No. Would you use nukes against saddam if he invaded, for instance Saudi Arabia too? Hardly.

so the size of Chinese nuclear forces ultimately doesn't matter at all.

I asked what kind of nation poses a direct threat to the US with equal capacity in nuclear arms. You answered china. Guess what? You were wrong.