You should visit Karachi but when things are better in Pakistan, right now its a mess. Plus if you do visit make sure you contact some local friend because you need someone who knows streets of Karachi or else you will get mugged very quickly. Street Food is the best in Karachi, beach is sh!t, but you will find all ethnic groups there, and if you are connected to right people you might even see the rich people night life stuff like parties, even Alcohol stuff.
Nah, I won't pick up St Louis anyway, Austin have decent size Muslim population so easy access to Halal/Kosher food, mosques, community etc.
I understand what you are saying, I am not saying they tell me every detail of their operations, like one black guy I met in Lexus showroom, he asked me if I am from India, when I tell him I am from Pakistan, he said I've been to Pakistan which kinda shocked me, I thought he might have been some Student from African country as I know people from some African countries come to Pakistani universities, but he said he was in Shamsi Air base, he didn't say much but when I told him that everyone knows that American operate Shamsi base he was shocked.
Now to answer your question, yes there are always people who will be there to replace the soldiers, in fact jhungry mention the same point, but thing is I don't believe that soldiers don't have a choice, they always do. Plus a lot of people here always talk about the how US soldiers are in difficult situations in Iraq or Syria, my point is why are your soldiers there in the first place? you have no business being there except create trouble, or steal resources or spy, no soldier is serving his country by being in a country that hates his presence and he is there to enforce his country's policy by using violence.
I hope you know that every military personnel be it American, Pakistani, Indian or any country has been brainwashed and indoctrinated to a degree, Armies pick up such young minds who are easy to manipulate, violent in nature and have ethnic or racial superiority complex, because its easier to convince them to go kill women and children (people of color) because they are a "Threat" or you are doing this protect your race, religion or western supremacy, either way in the end majority of Military personnel are brainwashed.
The day Americans start to believe that other people lives are as valuable as their own they might refused to go overseas to fight and kill innocent civilians, maybe at some point people will realize that the biggest threat to US is from within, you can protect America very easily but its America who keep bullying and invading countries that create resentment against America/Americans, you want to live in a peaceful world and with peace, stop calling people you don't like Terrorists or invading other people countries because Israel said so or you want to steal their resources or just you believe they are uncivilized.