Numerically, with the exception, I suppose of the people who originated in New France, now Quebec, the French have not made that much of an impact. Culturally and politically, however, the French impact on the USA has been large.

The story of the French in America is a story of what could have been.  While the British were huddled along the Atlantic coast and the Spanish were occupied with the Southwest, French voyageurs spread out from the commercial centers of Montreal and New Orleans in the 17th and 18th centuries.  These merchants created a vast continental trade network with the various First Nations.  Towns like Detroit and St. Louis were established as links in this system.  Alas, it was not meant to be as the British conquered New France in the Seven Years War (French and Indian War).  French-speakers were pushed back into almost reservation like status in Quebec and Louisiana.  Manifest Destiny absorbed those who remained outside of these core regions.  While later Canadian immigration injected some Frenchness back into the gene pools of New England and Michigan, the main legacy of the French is the dozens of place names throughout the country.  Influence grade of 2 stars.