Where to begin...?
Let's see... If I were Tom Clancy, and starting off with Jack Ryan's statement that "[B]esides, the Philippines has the strongest claim on those islands, we'll support them" masturbatory fantasy (see Bear and Dragon shitfest), the US (in a cozy relationship with the Philippines), decides to unload a lot of its Superbugs and Falcons because the JSF is such a Great Success Story on the Philippines, at bargain prices (never mind that most of our "modernization budget" is geared to soldiers' housing, uniforms [which explains the large number of varying camo patterns that surpasses that of the US military], and karaoke machines). So, from OV-10s and the flying coffins S.211s (yep, we have them RETAC), Manila gets several squadrons of Falcons and Superbugs, complete with the latest AIM-9 and AMRAAM. We also get OHP FFGs, and (OMG!) M1A1AIM Abrams tanks (plus Bradleys and ZOMG! Gavins!) to strengthen the Philippine Navy and Army respectively. The Philippine MARINES(!) will be given the AAVP-7 too.
So... China, alarmed by the .mil build-up of the Philippines, decides to fly the flag, Varyag-style, in the Spratlys. A (taking a page from Dale Brown's other masturbatory fantasies) Royal Dutch Shell exploration vessel in cooperation with the Philippines, strikes gold (rather oil) in the Spratlys. Varyag is nearby. It strikes, and PLAN MARINES(!) who were disguised as innocent fishermen living in those PLAN structures at Nansha Dao (never mind that those structures have 76mm guns, secure comms, AAA) strike hard and fast at the puny Philippine military outpost at Kalayaan Island.
The PAF, with its 2nd hand 'bugs and Falcons, strike back - with devastating results (for the Philippines). Meanwhile, our .gov contacts the US of A and waves the 50+ or so old Mutual Defense Treaty and says Uncle Sam, we want those who tanked, flew, and marched for Sam and were paided a bonus - plus MARINES(!) - to come help us.
Uncle Sam obliges, seeing that this nekkid aggression by China is, well, nekkid. So CINCPAC sends a couple of SSNs, sinks the entire Varyag fleet and a couple of PLAN subs to boot, all is well, and the Philippines and USA go to bed.
Oh, there's a love story somewhere there involving a Filipina and an American (MARINE[!] of course), if Tom Clancy had his way....
China rules. Vietnam will, IMO, strike back the hardest (but fails), Malaysia will make a half-hearted attempt (sees its claim in the Spratlys as not worth the cost), and Taiwan will look on, saying "We should've been there first!" Philippines will, most probably, raise hell in the UN, making loud speeches on nekkid aggression and wave the MDT before the USA who will, most politely say, "shove it up your ass" to whoever is our Fearless Leader at that reality (if it's our current Fearless Leader[TM], he'd probably pave the way for Varyag with a red carpet and wave the PRC flag
I really don't think the USA will go to war with China over the Spratlys. Not even send a sub or two to go do some fishing. They'll raise the alarm level, PACFLT ships will be deployed, US forces in Japan and SoKor will be put on alert, but no shooting war between the US and China. A region where ownership of the islands is iffy, State Department will pro'ly say "Well, China has the force to backup their claim, no contesting that." Much like Israel and the Golan, sort of.