Hmm...I think Gavriel D. Rosenfeld's "The Reception of William L. Shirer's the Rise and Fall of the Third Reich in the United States and West Germany, 1960-62" might actually shed some light on this matter. Check it out:

http://www.jstor.org/stable/260957

To summarize from pages 99-105, Rosenfeld states that almost immediately after the war ended in 1945, enmity between America and Germany--at least West Germany--began to recede because of the necessity of presenting a united front against the Communists during the Cold War. Now, as Rosenberg also notes, there was a time in the 1950s when people in both countries had begun to discuss the Holocaust and Germany's conduct in the war more openly, and in Rosenberg's words, Americans "began to wonder if Germany was an ally worth dying for." Still, he also points out that American-West German relations warmed up afterwards at the end of his article (p. 121), and in general the course of the struggle against the Soviet Union made it prudent for America to downplay the fact that it had once been at war with Germany, in order to strengthen ties with West Germany. This article in a political science journal adds some further nuance to this conclusion:

http://www.jstor.org/stable/pdf/23736495.pdf

To paraphrase Markovits' assessment of the optimists about Germany on pages 154-160, West Germany's successful integration of itself into the global economy, and the way it had proved to be a reliable trade partner to the U.S as well as a helpful ally in the Cold War, made many Americans less suspicious of it and more optimistic about its chances to become a peaceful, contributing "citizen of the world" by the 70s and 80s. Now, many Americans also thought that a unified Germany might become a worrisome trade rival, but the optimists didn't fear a resurgence of the Reich. As Markovits pointed out, some pessimists did, but as time went on and Germans became known for efficient engineering and solid products, anti-German sentiment declined as well.

Sources Cited:

1: The Reception of William L. Shirer's the Rise and Fall of the Third Reich in the United States and West Germany, 1960-62 Author(s): Gavriel D. Rosenfeld Source: Journal of Contemporary History, Vol. 29, No. 1 (Jan., 1994), pp. 95-128 Stable URL: http://www.jstor.org/stable/260957

2: Germany and Germans: A View from the United States Author(s): Andrei S. Markovits Source: German Politics & Society, Vol. 13, No. 3 (36) (Fall 1995), pp. 142-164 Stable URL: http://www.jstor.org/stable/23736495