US is self glorifying about WW2  but it is enough to cause annoyance to many Europeans against the US over it's own opinion on it's activities during WW2.  America's late arrival in the war is not something they should boast about.

In the film Saving Private Ryan (based on a true story of a British expedition to rescue British prisoners), where an all-American ground force takes on Germany; whereas America sent very few soldiers into war. America only began to send men into the war against Japan after Pearl Harbour, and the numbers and aid that America put into the world are pale in comparison to the massive war efforts conducted by Russia (who crushed Germany with 20 millions of ground troops), France (for it's bitter, endless and determined self defence) and the UK. The UK's air force and special forces were consistently very brave and effective (even though some of ground invasions of Germen held territory were ludicrously ill fated). 

America did supply vast amounts of material goods, but it did not commit, or it's soldiers, into combat wholeheartedly. America's most consistent aid was against the Japanese, and not until Japan attacked America directly, and even then America eventually resorted to the massively indiscriminate nuclear bombs rather than "waste" men on resolute Japan. 

America appears to be very self-glorifying, and there are multiple generations in the UK, France and Europe who upset and angry with America's rewriting of history. Russia's men, France's entire population, and UK's air force, were the principal opponents of Germany, aided by American equipment, for which we are grateful, but it annoys some people (it used to annoy me, as you can tell, until I sold my soul) enough that I consider it a reason, related to patriotism, that people hate the USA.