Both the sentences are accepted.
In the second sentence, I weren't American is using the subjunctive mood, which is correct, in that case (I read the sentence as I would do it, if I weren't American.). The subjunctive mood is nowadays less common.
As reported by the NOAD:
The subjunctive is used to express situations that are hypothetical or not yet realized and is typically used for what is imagined, hoped for, demanded, or expected. In English, the subjunctive mood is fairly uncommon (especially in comparison with other languages such as French and Spanish), mainly because most of the functions of the subjunctive are covered by modal verbs such as might, could, and should. In fact, in English the subjunctive is often indistinguishable from the ordinary indicative mood since its form in most contexts is identical. It is distinctive only in the third person singular, where the normal indicative -s ending is absent (he face rather than he faces in the example above), and in the verb to be (I were rather than I was , and they be rather than they are in the examples above). In modern English, the subjunctive mood still exists but is regarded in many contexts as optional. Use of the subjunctive tends to convey a more formal tone, but there are few people who would regard its absence as actually wrong. Today, it survives mostly in fixed expressions, as in be that as it may; far be it from me; as it were; lest we forget;: God help you; perish the thought; and come what may.