The U.S. has strategic allies and interests in the region e.g., access to oil. Abdication or isolation is not a practical policy. Having said that, military strikes are not necessarily the best way to address the problem. Even if the U.S. does not pursue, much less succeed in implementing crippling sanctions on Iran, the U.S. can sell arms to help maintain the region's balance of power and construct an effective deterrence regime were Iran to develop a nuclear waeapons capability.
The problem, to date, is that the U.S. approach has been muddled. Sanctions fall far short of those that would be necessary to impact Iran's strategic petroleum sectors. Even total financial sector sanctions fall far short given that Iran's financial sector is not globally-connected. In addition, there is no evidence, to date--even post-Wikileaks disclosures--that the U.S. has even discussed the outlines of a deterrence approach. Given a combination of factors ranging from past flaws in U.S. military planning to the risks associated with Iranian retaliation, Saudi Arabia has little reason for a great deal of confidence in the viability of a U.S. military approach. Hence, the new Saudi effort aimed at accommodation with Iran is underway. Whether that approach ultimately safeguards Saudi Arabia's vital interests remains to be seen and real risks are involved.
However, even if Saudi Arabia safeguards its own vital interests, that approach may not safeguard vital U.S. interests/strategic allies. Arguably, Iran could remove Saudi Arabia from the equation, and that would complicate efforts by the U.S. to protect its own vital regional interests/strategic allies who have not reached an accommodation with Iran. The balance of power issue would still remain and that has long-term risks for the U.S.