(1) The US is going to draw down its troop levels from Western and Central Europe. This will negatively impact their economies. And if they want to have military power they are going to have to pay for it on their own nickel..er..Euro.
(2) They have made no effort to assimilate their immigrants, many from the middle east and Africa. Those non-assimilated immigrants have a significant Islamic component. By deliberately keeping them non-assimilated, it encourages them to move to the more radical Islamofacist Wahhabi wing of Islam.
(3) By pissing off American, American consumers will think twice, three times before buying French...and possibly German. This will negatively impact their economies.
(4) The European Union political structure is corrupt and bureaucratic. Where they are effective they just produce regulations that bollux up their economic engines. Where they are corrupt they just waste money and cause political apathy, worsening their problems.
So -- screw the Europeans. Time to let them stew in their own Socialist juices for a while without support from the American taxpayer. Maybe after they suffer for a while (probably 20 to 30 years) they will figure out they are on the wrong path. In the meantime, we can focus on our own interests.