George Friedman writes:

The withdrawal of U.S. forces has had a profound psychological impact on the political elites of the Persian Gulf. Since the decline of British power after World War II, the United States has been the guarantor of the Arabian Peninsula's elites and therefore of the flow of oil from the region. The foundation of that guarantee has been military power, as seen in the response to Iraq's invasion of Kuwait in 1990. The United States still has substantial military power in the Persian Gulf, and its air and naval forces could likely cope with any overt provocation by Iran.

But that's not how the Iranians operate. For all their rhetoric, they are cautious in their policies. This does not mean they are passive. It simply means that they avoid high-risk moves. They will rely on their covert capabilities and relationships. Those relationships now exist in an environment in which many reasonable Arab leaders see a shift in the balance of power, with the United States growing weaker and less predictable in the region and Iran becoming stronger. This provides fertile soil for Iranian allies to pressure regional regimes into accommodations with Iran.

The formula is not complicated: A strong Iran (and, God forbid, a nuclear Iran) would make it clear to smaller Arab powers that a peace process with Israel is not in their best interests. Weaker powers will abide Iranian wishes. The two-state solution is already on life-support; a strong Iran (combined with ineffective Palestinian leadership, and thickheaded Israeli leadership) would spell an end to the hope for a decent solution.