The Department of Homeland Security is a Cabinet position that was created in 2002, out of response to the terrorist attacks of September 11, 2001.
increased urbanization which led to expansion
Italy, Greece and France have never been under the Islamic Empire (or any Islamic rulers as far as I know).
Spain was under Islamic leaders for a long time and there was a period of re-conquista later, when the land was re-conquered by the Christians. And in 8th centrury Spain was in fact part of the Islamic Empire.
