North Carolina is an employment-at-will jurisdiction. You can be fired at any time for any reason. The only time that you can successfully sue an employer for wrongful firing is if you can show that you were fired due to unlawful discrimination or unlawful retaliation. It is important to focus on the word "unlawful" because most forms of discrimination and retaliation are lawful.
I do not see anything in your post that suggest the termination was unlawful. However, you may want to consult with an experienced employment attorney just to be sure.
I am an experienced attorney focusing my practice on employment law in North Carolina. This post/response is not meant to constitute legal advice.