I am studying in college in the United States. Because I did not take enough 12 credits in one semester, my F1 visa was invalidated.

First of all, American university undergraduate requirements for all international students are that they must take at least 12 credits each semester. 12 credits is also one of the standards for full-time students. If you do not take 12 credits, you will be required to take at least 12 credits. American universities and U.S. immigration laws stipulate that your I-20 will be canceled. If your I-20 is canceled in time, your visa is still valid and you must return to your country. So not choosing 12 credits is very serious.

What needs to be done now is,

Communicate with the school to discuss whether there is a chance to get a new I-20. If you get it, you can still stay in the United States to study

If you cannot get a new I-20, you need to return to China within the time specified by the American university for leaving school and leaving the country. After that, you can re-apply to an American university, get a new I-20, and return to the United States to study. And if your visa is valid, you do not need to re-visit.

If you fail to leave the country within the specified period and violate U.S. immigration laws, it will affect your next entry or visa, and customs may refuse to let you enter.