Why do Americans falsely take the credit, even when other Forces secured Victory?

Too numerous to mention, but one example from the Gulf War was of HMAS Kanimbla single handedly detecting & capturing an Iraqi Shop laddened with Marine explosives ready to be deployed and take out the US Naval Force there! That was an the Australian Navy who boarded & discovered the bombs, not AMERICANS! Almost every time its the same with Americans, from WWII & Japan to the crap about freeing Europe of Hitler! Why do Americans overstate their achievements and take the credit of others?