I read the following quote recently by a Muslim woman who made this point: "We submit to God, no one else."
I find this revealing in a number of ways. One is the idea of submission. Please note how this attitude will encourage one not to adapt to any new environment. Submission is giving in, so why would immigrants (who believe that they come from a legal system that was set up by God) submit to the new culture and environment (Set up by humans) they now live in? In addition, how could anyone expect someone to prosper in the new environment with this attitude?
Implied in this quote is the idea that Islam as a form of governance trumps all the governments in that the Koran is the direct word of God. Seeing as she submits only to God, then it is implied that she submits only to Islamic law, which is spelled out in the Koran. Seeing as God set up the Islamic system of laws and government, they are perfect and not changeable. This attitude is commonly seen throughout the Islamic world.
If this person who was quoted believes in religion as we in the 'West' see religion, we would understand that she is talking about personal behavior, not government. However, Islam IS a form of government with a complete legal system. As such, it is implied that she will not submit to the new rules imposed by a different government. (Other than Islam) And that she will actively work to make the new environment change into one that is 'submitting to God'. In other words, the adapted country must submit to the government and legal system of Islam.
The spark for violence is that Islam is a complete way of life. I have studied the biographies of thousands of soldiers. They became soldiers to protect their way of life. History is full of wars fought because of change to way of life, or threatened change to way of life. This is a major contribution to the many wars and violent confrontations where Islam is in contact with the rest of the non-Islamic world. This is primarily because Islamic way of life as spelled out in the Koran and Islamic law is hostile to just about everything else. If you have any shred of doubt, do not take my word. Look at Islamic law. You will not need to look all that closely.