I’m 17 and live in the United States. Can I apply for a fiancé visa for my fiancé.

The answer is maybe.  If one of you is under the age of 18, you are likely to be considered underage in the United States. Your legal ability to marry will depend on the laws of the state where you plan to get married. Each of the 50 U.S. states sets its own rules, and you will need to research them. For example, you may find that in one state you must be 18 years of age to marry, while in another you can marry younger if you can show the consent of your parents. Assuming that you are of legal age to Marry,  you still must get around the obstacle of filing a financial affidavit establishing that you have the minimum level of income to sponsor your fiancé.