Justin Vaisse's opinion
This relative absence of French-American political and social unity helps to explain anti-French sentiment in the United States. French historian Justin Vaïsse has proposed that an important cause of overtly expressed public hostility toward France in the United States is the small number of Americans of direct French descent1. http://www.politiqueinternationale.com/revue/article.php?id_revue=12&id;=228&content;=synopsis. While he acknowledges that this is not the direct cause of anti-French sentiments, he argues that it explains why these sentiments can be expressed publicly, without being seen as a gross violation of political correctness. Vaïsse contends that by comparison, the public display of such sentiments towards other ethnic groups or nationalities would be met by strong disapproval. He proposes that as France has no powerful and organised lobby to defend it, it is socially and politically acceptable in the United States to express negative sentiments of the FrenchPierre Verdaguer, "A Turn-of-the-Century Honeymoon? The Washington Post's Coverage of France", French Politics, Culture & Society, vol. 21, no. 2, summer 2003.
 Just to answer, I've read before that the proportion of french descendant in the US is way higher than thought because as the french colonized the New World at the same time as the Brits but got outnumbered pretty quickly, they were mixed into the mainstream america. However it's true that since most of them lost traces of their heritage no lobby exists nor defends them as they don't represent or try to represent.