First off, oil is a global commodity, so it's not true that you can just isolate yourself from global price movements. Second, how many soldiers in the Chinese

First off, oil is a global commodity, so it's not true that you can just isolate yourself from global price movements. Second, how many soldiers in the Chinese PLA or PLAN have ever fired a weapon against a hostile force? The US has spent the better part of two decades in an active war environment. For better or worse, there's value to having actual experience with large-scale invasions. It's not being "ground into dusty incompetence", it's being battle-tested. Third, the US military doctrine since WWII has been about fighting two wars at once. We can certainly protect Taiwan and the Persian Gulf at the same time. If we couldn't, then any intervention wouldn't be credible because the second we invade a nation, all other strategic objectives would be at risk.