Why are Americans Joining Islamic Groups?

I was asked today by a coworker if an attack could be made by the group ISIS on American soil.
Of course it theoretically can happen. As traction is gaining with ISIS and it seems a "No War" situation is growing ever smaller, American Citizens are joining the ranks of this group. The Department of Justice has apprehended a few hopeful "wannabes" as they either tried to leave or have returned from places like Syria and Iraq. Recently one was even killed fighting with an ISIS linked group. We have seen in recent weeks tweets and news stories of people claiming to be ISIS members showing a flag and note at the gates of the White House and another leading police on a car chase with a ISIS flag displayed out their car window. These could be legitimate members of this group or another, and it could just be people claiming to be but not actual members of  these groups wishing to cause a stir and strike fear in the minds of the citizens.

This leads us to the title point "why would these people join the ranks of a group notably violent towards religions and peoples of certain geographical locations? Why would they give their lives for a cause of violence in the name of some distorted religious view?

It may be those that have found their own view of Islam in whatever fashion they accept it or it could be in some odd way a chance to gain notoriety in themselves. I do not presume to know what drives people to the choices they make. But it is an interesting question to be sure.

In talking with this co-worker he had also asked if any event took place do I think it would be a large scale attack or small. I have to say that for myself I do not really worry too much of the scale of what may or may not happen. It may be small on the scale of a suitcase explosive or it could be on par with a 9/11/01 attack, I think it is a non issue at the size or scale of whatever happens. I don't think it would take much at this point to excite Americans into a religious genocide against every self-described follower of Islam. With the amount of fear conditioning and propaganda being broadcast it wouldn't take much to start a war on all of Islam, in my opinion, although I surely hope I am wrong.