Sigmund Freud’s shadow hung over the Twentieth Century like a dark storm cloud (F. Scott Fitzgerald’s ditzy heroines ca. 1930 were “hip to Freud”) , and it was Freud’s nephew Edward Bernays who invented the science of public relations which rules us today.
During WWI Bernays, along with the two other founders, Walter Lippmann and the Rockefeller press agent Ivy Lee, were in charge of America’s internal propaganda effort.After the war Ivy Lee worked for the Nazis, while Bernays worked to gain the right to smoke cigarettes for the beaten-down women of Puritan America, who were never allowed to have any fun.
Lippmann, already the brains behind the New Republic tabloid, became one of the  elder statesmen of the Democratic Party and one of the founders of neoliberalism. And finally, in 1956, Ivy Lee’s nephew William Burroughs revolutionized American literature. That’s a lot of culture to pack into 40 years.
That’s all you need to know right there. Various other Americans were once thought to be culturally important in some way, but in the long haul none of them amounted to a hill of beans.