In the United States today, I would argue that class is used by many to try to define what a "real" American is. This idea of class is not really an economic one -- it is more of a social definition. There are many attempts to define "real" Americans as those who are not particularly intellectual and who do not engage in "highbrow" activities.
In America, politicians tend to try to emphasize that they are somehow connected to the "common people." These are the people who are portrayed as real Americans. Real Americans are those with a high school diploma or, at most, a college degree. They are people who like to drink beer rather than wine. They like to bowl or hunt rather than to play golf. They prefer NASCAR races to operas. We are told over and over that those people are in some ways more truly American than the more "elite" types who do not share their values.
In these ways, there has been a real attempt to define Americanism based on class. There has been an attempt to portray these "common" or "middle class" people as the real Americans and to say that elites are not real Americans.