This can be interpreted in many ways, and each person may have their own opinion for when the US was at its height. I'd say in between 1918 - NOW. World War I established the US as a major world power - but the US did not assume this role until after WWII when it was 1 of the 2 Superpowers. In between the time of WWI - WWII America soared - the Roaring 20s were good times, but the depression was bad. BUT the US made the BIGGEST comeback in WWII - after joining the war in late 1941, Ameerica militarized super fast and became the largest manufacturer in the world! And in both wars, America's entry in the war helped turn the tide of the war - in the Allied powers' favor. After WWII, the Cold War struck but America was still at the top of its game. Military spending soared up super high because of atomic weapon manufacturing. The greatest presidents - although they've had their flaws - have passed through the White House since the Cold War (FDR died, and Truman came, Eisenhower, Kennedy, Johnson, etc...) America, although involved in some shady business to contain the spread of communism, was definitely a super power in the field of foreign affairs. Culture, although you didn't mention it, also soared at various periods of time - the Roaring 20s, escapist media, 50s religious culture, 60s rebellious culture, it's all influential.