I agree, the anglo-settler nations are a formidable threat when put together, possibly greater than any threat China has ever seen. Hopefully in the future they drift away from each other culturallyProtect Israel and Saudi from what exactly? You think Iran is going to invade the entire Persian Gulf and Levant? I doubt they are even capable under obvious Arab/Israeli constant air superiority.
If America concentrates its forces in the Pacific I doubt anything bad happens to her allies. The worst may be Russia posturing more in Ukraine, and to America the Ukrainians losing more land to Russia is worth the exchange for eliminating China.
China should always base her assumptions on worst case scenarios, that is, the full force of the USA, Australia, NZ, Canada, UK, India, Japan, Vietnam be brought to her shores/seas/skies/land combined.