American and Muslim scholars wonder why President Obama didn't choose to speak to the world's Muslims from the world's most populous Muslim country -- Indonesia -- which happens to be more democratic than Egypt, where Obama touches down on Thursday.  The answer is two-fold: Egypt is a critical American ally, and not just because it took some terrorists off of our hands and tortured them. When it comes to dealing with Iran, Egyptian public opinion constrains the ability of Hosni Mubarak's government, which disparately wants to keep "the Persians" from going nuclear. As it stands, Mubarak has to cast the Israeli-Palestinian conflict as more troublesome than Iran, even though he probably believes the opposite. When it comes to vital American interests, a more pro-American Egyptian populace will give Mubarak leverage. A harsher American line against Israeli settlements and Obama's vocal endorsement of a two-state solution have also helped.  (I'm not saying that Egypt doesn't believe that an agreement between the PA and Israel isn't a necessary first step, just that, so far as threats to the Arab and Muslim worlds go, Tehran outranks Israel. An unstable Gaza and West Bank are just as dangerous in the near-term.)