One consequence of a Mecca nuke is that there will no longer be a nation called Saudi Arabia. The United States would have to administer the oil with a coaltion of allies.
Unfortunately I dont think we would have a coaltion of allies if we nuked Mecca. 10% of France is Muslim, Thailand has its own problems with Islam...the Arab community would be burning down cities around the world...nobody would join our coaltion of allies even if they secretly accepted our nuking Mecca and they would not even secretly accept our nuking Mecca because they still think we were wrong nuking Japan.