China has nothing like the sort of shipping required to mount an effective invasion of Taiwan.
http://www.globalsecurity.org/military/world/china/navy.htm With 40 odd true amphibs, they aren't going to be getting much of that huge army across the straight, unless they plan on packing them into various frieghters and the like...

Taiwan has a standing army of 200,000, not to mention 1.5 million reservists, all trained specifically to repel a Chinese invasion. Without a huge increase in amphibious shipping and marines, China would be acheiving little more than putting its ships and men into a meatgrinder trying to invade.
Note too that China has no Brahmos or Yakhonts at present, they have merely been offered for installation on its two destroyers ordered from Russia. These ships are still under construction. Even when completed, that will give the Chinese a total of two ships equipped with Yakhont. At present China has two -- count 'em -- two modern destroyers (the US has about 80). Lets also consider China's 'ultramodern' SSN fleet (5 ships):
"The Han-class SSNs are noted for problems, including high internal radiation levels and an inability to fire missiles while submerged, which compromise their operational effectiveness and their wartime utility against ASW-competent adversaries. The lead boats (401 & 402?) suffered radiation problems which were thought to have been solved after extensive refit. But since the late 1990s they appeared to have become inoperational. According to some reports, as of 2000 only two of its Han-class SSNs remained operational, despite the extended re-fits to the units of this class. "
Source :
http://www.globalsecurity.org/military/world/china/type-91.htm China's solitary SSBN is no longer operational, either.
As for China's air force, where is it going to acquire all the ramp space near Taiwan to get even the smallest fraction of its aircraft in the air at one time? Most of China's aircraft will be low on feul the minute they even reach Taiwan. They have acquired 40 Su-27s and plan to build more, but this is still very much a future threat.
There is certainly no need for anyone to lose any sleep worrying about a Chinese invasion of Taiwan; the Taiwanese could probably stop it themselves without any aid from the US at all.