I hear this a lot. I'm going to ask some key - and serious - questions to some of your points:
Why? Because they have never sat by. Islamic fanatics have been targeting America and its citizens for half a century ... see below.
Why do they have the motivation? Because they hate us. Right or wrong. For some it's rivalry (China, N. Korea). For Islamic extremists, they have hated us since the day we backed the formation of the state of Israel. And to this day our support of Israel has incurred their undying hated. Even the moderates in the Middle East are not happy with our support and policies regarding Israel. N. Korea, in short, wants the entire Korean peninula for itself. They hate us because we have stood in their way for nearly 60 years and have tested us often over the last few years to see how committed we are to S. Korea. China hates us because we back Taiwan to the hilt. China has promised to retake Taiwan someday -- and we are sworn, like we are with Israel, to come to their aid if they are attacked. Worse, China is eating our lunch economically, holding a ridiculous amount of U.S. debt (we borrow 42 cents from them on every dollar we spend). Additionally, China is developing next-generation military hardware (much of it stolen and spied from us) that could put them on a level playing field with us in a military confrontation. Scary. China has the wealth and coerced support of more than a billion people to feed into its growing and evolving military.
Why? And what role might have the US played in creating our own peril? The term fanatical should cover that. Because that's what they are. They believe they are doing God/Allah's will in fighting evil. Again, our support of Israel, as well as our friendship with Britain (which used to hold great colonial sway in the Middle East) inflames the religious and, yes, nationalist fervor. Iran's regime has had us in their crosshairs since coming to power in 1979. They hated our support of the Shah and they hate our continued support for Israel in its struggle with Hamas, Hezbollah and Palestinian statehood. But Iran, at least, is one of the most evolved of the Middle Eastern nations. Despite falling under the thumb of a radical theocracy, many Iranian people desire democracy or some sort. They chaff under the rule of the Ayatollah and the ruling clerics. By all accounts, many typical Iranians fear that their government is dragging them into a conflict with the West that will lead to their destruction. We should pray for the day that the Iranian people overthrow their government and take control. It worked in Tunisia, it's worked in Egypt so far (but the jury is still out), it worked in Libya, and it will ultimately work in Syria. You're correct about nationalism being a motivator. That is what led to the Arab Spring last year -- Arabs as a people, not as Muslims, taking out their anger, not on the West, but on their oppressive governments. Again, if a revolution begins in Iran, we should support it fully. The time of dictatorships and authoritarian regimes is slowly becoming extinct. But the few that remain are desperate to hold onto power.
Religious extremism is incredibly dangerous, no doubt; it isn't, however, the main driving force - it's but a tool for the shepherds to heard the sheep to arms. What motivates the shepherds? Nationalism. The Tigers of Tamil of Sri Lanka, for example, are a secular group, but are responsible for far more suicide terrorism than any of the middle eastern groups. I agree that regimes often use religion as a tool to lead their fanatically loyal, but ignorant, followers to do some very terrible things. But what of terrorist groups like al-Qaida? They did quite a number on us on 9/11 in the name of religion, These guys went down with their airliners screaming "God is great!"
You know what gets nationalists up and armed more than anything else? An enemy - perceived or not - in their backyard. ...how long have we been in their backyard? Yes, we are indeed in their "backyard" and have been for the last decade. The answer as to why should be obvious. The radicals in the region brought it upon themselves. We had no boots on the ground in Iraq or Afghanistan BEFORE 9/11. If they don't want us in their backyard, then perhaps they should try being reasonable, stop attacking innocent, INNOCENT Americans around the world, allow Israel to exist without constant threats of its destruction.