Getting back to the question, how does propping up Israel's military protect us - or anyone anywhere - from the possibility (perhaps likelihood) of China becoming the world's dominant economy over the next couple of decades?

The main strategic advantage is, obviously keeping China from gaining too much control over the oil resources of the region. The U.S. doesn't import much oil from the Gulf states anymore, but they're the largest supplier to the larger Asian economies - including not just our key allies in Japan and South Korea (which get more than 70% of their oil imports from the region), but China itself (which gets about half their oil imports from there. Having a multi-polar regional balance of power, with key players allied closely with the West and the US specifically, keeps China from consolidating control over a major source of its own energy imports but those of key strategic checks on their economic influence in east Asia. That by no means assures us that China won't become the world's dominant economy, but it's an important piece of any strategy to try to prevent that from happening.

As I noted in my prior post, the geopolitical importance of keeping Russia in check has indeed faded. As has the perceived importance of fighting the spread of radical Islamic movements. That causes people to more greatly question how necessary it is to maintain a big powerful ally in the area (relative to regional forces), given the diminished threat profile. It's a legitimate point. One would want to look at whether the waning of those threats is a durable, long-term change or whether it's important to maintain our footprint there to either prevent or respond to a resurgence of those threats in the future.

Given the continued, and likely continuing, importance of those energy resources to both the global economy and the nations we most rely on to keep China somewhat in check, we definitely have an interest in what happens in the region - even if you think that we no longer need to worry about Russia or threats emerging directly from the various terror organizations in the area. Whether that interest is large enough to warrant our continued involvement is a valid debate, but I think it's certainly large enough that we shouldn't dismiss as pretext those who argue that there are still material benefits from having an unabashedly West-oriented ally in the region.