In the last decade, the U.S. military has enlisted some 70,000 non-citizens, about five percent of all recruits. These foreigners made better soldiers than American citizens. The foreigners are tossed out during their first three months of service at half the rate of their citizen counterparts. After three years of service, 72 percent of citizens were still in uniform, compared to 84 percent of non-citizen troops. The foreign troops are more patriotic and work harder than their citizen counterparts. Non-citizen troops have another incentive, as they can apply for citizenship because of good service in the military. Any foreign recruit forced out for medical reasons (because of combat or non-combat injuries) can still obtain citizenship more quickly. Most foreign troops obtain citizenship as soon as they can while in the military, because many jobs require a security clearance and only citizens can get one of those.
For those who worry that these are foreigners doing a job Americans won't--or that we are creating a civil-military divide--we used to have a much higher percentage of foreigners in our military.
As far as I'm concerned, we should have recruiting stations abroad to bring in the Americans-at-heart who live in nuanced nations that don't believe defending Western civilization is any concern of theirs.
When our jihadi enemies recruit not from a national pool but from an international pool of recruits who fight us even though their own governments may be our allies, why can't we do the same?