A Muslim can't marry a christian or a jew, that is too general a statement. A Muslim man can marry a chaste female christian or a jew.

And in Islam the male is head of the household, so he controls the situation. He would treat her good like he does any wife, and obviously she would be briefed on the situation and not try and be a negative influence on him or his children. Otherwise it's not appropriate to befriend females in the first place. The wife is not a teacher or a mentor, and not someone that the man looks up to for instruction in life.

As for the topic in general, you should read the entire surat Al Maa'idah, interesting verses in there regarding kuffar in general. Notice all the verses stating how they will try to steer you away from your religion, and anyone who has had dealings with kuffar must have noticed this, especially if they are religious ones. I've dealt nicely at work with religious christians before, they will try and drop hints here and there that, you know, maybe this Islamic way of doing things is not correct. Or maybe this rule here is not ideal. Actually you can see we have a couple on here already in a huff about it and we're not even their friends.

Really when dealing with these people, the vast difference between you and them should make it clear you really are a stranger, as if from another planet because of just how different their ways of thinking are, and not in a good way. The things they are fixated on, the manner with which they view the world, much of it is rejected by a Muslim and extensive dealings with them should be avoided lest you be influenced. When you go to college I think it's safe to say you will see some Muslims who do have extensive dealings with kuffar and take them as friends. Their behavior and views are commonly heavily influenced and their walaa' and baraa' completely shot.