In the book "Conversations with Billy Wilder," Cameron Crowe reads an old newspaper quote from Hollywood's Golden Age to Billy Wilder in which a commentator observed the irony that the heart of the American Spirit was being captured onscreen by an Italian (Frank Capra), a German (Ernst Lubitsch), and an Austrian (Billy Wilder).
In reality, it wasn't just those three (although personally, I never felt Lubitsch catered to Americana) but much of Hollywood in the 1930s and '40s was composed of immigrants. Many Jewish filmmakers escaped to America to escape Nazi persecution and other filmmakers were pushed over to America because Hitler dissolved the country's prominent film industry and replaced it with a wartime propoganda department. Among the directors from Germany's Ufa Studio (which in some ways was more progressive than the United States) were Fritz Lang, Otto Preminger, Edward Dmytryck, Douglas Sirk and even Alfred Hitchkock who was British but interned with Ufa. They influenced the American film industry through their aesthetic. Without them, the film noir movement, which captured the country's pessimistic mood, would have never taken hold. Greg Toland, one of these German emigrees first infused the expressionist style into American films with Citizen Kane, but Billy Wilder fused that styling with the pulp novel mystery to create the first true film noir in Double Indemnity (1944) so he was a cornerstone of that movement to which Dmytryck, Lang, Preminger and others followed suit. But like the quote said, Wilder didn't just infuse the German aesthetic into American film, like some of the immigrant directors who stayed in the film noir genre.
He experienced the American dream, going from rags as a poor immigrant going through Ellis Island, to riches. He was transformed by it and was an ever-present observor of that dream. The Apartment, although considered a comedy, was a brilliantly dark satire about the sacrifices people are forced to make for that dream. Perhaps one can imagine Billy Wilder having been The Apartment's C.C. Baxter at some point in his life, having to sell his dignity to work his way up the corporate ladder at the Studio. Through tools of humor with Ball of Fire, romance with Sabrina, and blatant sexuality with Some Like it Hot he dissected the hypocrisy of a class in America. He also was proud of being one of the first to explore alcoholism in The Lost Weekend.
When Crowe asked Wilder about his thoughts on this quote Wilder said it was funny because he couldn't make a European movie. Consider the dud Irma La Douce, which he conceded was a failure because he just couldn't make Lemmon and Shirley MacLaine come off as European. Wilder had lived the American dream and it became an inescapable part of him.