What would happen if an American (or Israeli) dropped a nuke on Mecca?
Not the country-- an individual. The US government wouldn't do that unless something specific provoked it, like Saudi Arabian Islamic terrorists nuked Washington, and even then it would be doubtful. Israel would wait until they were nuked first. But if a terrorist group of Islamic extremists could fly planes into the World Trade Center, an American anti-Muslim extremist could theoretically smuggle in or drop a nuclear bomb on Mecca.
Well, if it was an American, I'd guess the US would immediately find all contacts of the individual and turn over anyone who had knowledge of or involvement in the plan for trial and execution. We'd also send as much aid as possible to the area, trying to make reparations and prove to the world that it wasn't our doing and we don't support terrorists.
Meanwhile the entire Muslim world would hate us anyway, and eventually, a world war would break out.
And if it was an Israeli, I'd guess Israel would also make reparations, but in a kind of half-hearted way, due to international pressure. Then there would be a war between every single Muslim nation and Israel, and possibly with the US allying with Israel.
Meanwhile, what would happen to Mecca?
I am reminded of the Ganges River in India. Hinduism states that the Ganges is sacred, and bathing in it helps a person to obtain salvation. Drinking the water at the end of your life will take your soul to heaven. Spreading of ashes there is also holy.
But the Ganges River itself runs through some of the most populous areas of India. It is thus filled with untreated raw sewage, runoff from the leather industries, partially burnt or unburnt human remains, and livestock corpses. It is a steaming cesspool of filth and disease, and the Hindus still come. They come, they bathe, they get sick. They touch this vile, polluted, revolting river because they consider it holy.
So I believe the Muslims would still go to Mecca. They would go to the radioactive ruins of Mecca and then die slowly of radiation poisoning. Not all of them, but many. So nuking a site that people of a faith MUST go to, the terrorist would be committing a crime against humanity ten times worse than Hiroshima and Nagasaki, because you would kill not only the million or so inhabitants, but also the pilgrims (especially if it was during the hajj, with four million pilgrims), and give radiation poisoning to millions of Muslims who would try to go at some point before the fallout cleared. Most Muslims would not go before they had children and were old and able to die, so the population would not decrease.
The trouble is that the ground itself is holy. It's not just the Black Stone and the Zamzam Well and the Kaaba. That is the land where Muhammad walked, and thus, it would be holy even if to touch it was to guarantee a long, slow, painful death.
I have to say, if I ruled the world, I would turn Mecca into the Muslim version of the Holy See-- a separate, unique state not controlled by the country it is within. I'd also say they had to allow non-Muslims to visit (but not during the hajj, because of the sheer volumes of pilgrims they already must handle). I would love to see Mecca some day-- I would even wear a hijab for respect if it was asked of me-- but I never will be able to, because Saudi Arabia has banned all non-Muslims from entering the city. Even if that were not the case, I would be hesitant to go anywhere in Saudi Arabia because of Sharia law.
It saddens me to think of all the ancient holy cities-- Mecca, Jerusalem, Bethlehem, Cairo, and more-- that I would not be safe in as a woman, as a American, and as a non-religious person. So much history, and it is trapped in a place filled with hate and war. It feels sometimes like the land there is just so sick of dealing with humanity that it almost NEEDS fallout just to give it a chance to breathe, to take a break from tens of thousands of years of civilization. And yet, what we would lose would be unbearable, for while Africa is where we were born, the Middle East is where we grew, and where we became what we are today.