The reason the tafsir is as it is, is because there is a verse telling the believing men and women to not marry the idolaters (I think in Arabic it said kufar, I can't really remember).
Actually there's no verse in the Quran that says a woman can't marry a non-muslim man. It's supposedly in the sunnah (prophetic tradition) although I can't find a hadith supporting this view which is odd so this ruling may as well have been derived from qiyas (analogy).
In a different verse, it says a man can marry a woman of the book. There isn't another part that specifically says a woman can, but some people say that this can allow woman to marry men of the book because while it wasn't specifically mentioned, some other verses that use male pronouns include women in them as well.
The verses are 2:221 and 5:5