It's unknown, or unverifiable. Large numbers of African Muslims were enslaved and transported to North America, so Muslims have lived in North America for much longer than the USA has existed.

Fun fact though! Morocco was the first country to recognize the United States, in 1777. It is thus the USA's longest diplomatic alliance. I do not believe they sent dignitaries until some years later, though.

Apparently, there was a community of Moroccans in South Carolina in 1790. makes sense when you think about it - Northwest Africa is closer to the USA than most of Europe.

Just to clarify, do you mean to ask about the first Muslim in America following July 4th 1776 or do you mean to ask about the first Muslim to discover the land that is now known as the US?