Drive fear into America by de-stabilizing their economy.
If it's one fear americans have it's the loss of their personal wealth.
The US economy is plagued by stock market fears. It's foundation is rocked by financial scandals, and corporate greed. The average p/e multiple is historically 50% higher. Since the average american is over leveraged, and the economy is sputtering, a oil price surge will shock the US financial system. The dollar would sink, and foreigners would sell their investments, deepening the spiral downwards.
The effect would also be multiplied by the bursting of the housing bubble. It is the most vulnerable, an inverted pyramid waiting to be pushed over. Presently it's a $3.1 trillion mortgage on a base of less than 0.02% reserves.

Fight the smart war use your guerrilla weapons and kill the american beast.