There is a difference between those who come here to be a part of this country and those who do not. When in the USArmy I saw a lot of people who were under the old Lodge Act. Mostly Europeans, but I also saw some KATUSA and they were ok.
These people have unique knowledge and skills that US Army can use on the ground. By coming in and being US Military they earn their citizenship they are invested in the US and will be good citizens. Consider how many native born US Citizens will not serve. Think of liberal college students who are 'too educated' to serve.
My big concern is how do we check out these new soldiers to see if they can be trusted?