"Step 1: move a lot of Muslims into the Western Countries.
Step 2: Get the countries to give them autonomous areas
Step 3: Make these autonomous Muslim areas grow, until they squeeze out the rest of the areas and take over the countries."
These steps took place most recently in Kosovo, and were supported by military attack during the Clinton administration, with the verbal agreement and support of Bush Jr. as per his own words. The Muslims moved into the Kosovo area, began to breed like rabbits, until they multiplied enough to take over the area, and succeeded, with the help of this country via the Clinton Admin, to become autonomous, and are now trying to establish their own state in an area that was once part of ancient Serbia.
The same will happen here in our southern states of Texas, New Mexico, California, and Arizona, by the Mexican illegal immigrant invasion, and they will spawn multiple children until they too will "own" these states, and regain by propagation that which was lost to them, territory-wise, during war with Mexico.
The "reconquista" that you refer to is a possibility as Texas, New Mexico and California will one day be mostly Mexican ethnicity. However, even that scenario is not as scary as the Islamic takeover of Europe. The Mexican immigrants are not members of a religion which believes it is a holy act to become a suicide bomber, most are just coming here to work.