Years from now, when the history of Barack Obama's much-maligned Asia "pivot" is written, he may owe a debt of gratitude to an unlikely ally: Xi Jinping.

The Chinese president is, of course, vehemently opposed to the U.S. rebalancing its focus toward the East. Hardliners in Xi's Communist Party believe the U.S. president should stick to his own neighborhood and leave the world's most dynamic economic region to China's suzerainty. But Xi's ham-handed efforts to assert himself in Asia are having exactly the opposite effect.

Aggressive Chinese maritime claims are driving Vietnam into Washington's arms and leading Filipinos to welcome back the U.S. troops they once relished sending home. An apparent assault on Hong Kong's cherished freedoms is alienating one population that has reunified with the mainland and another — Taiwan's — that increasingly seems to dread the prospect.