There's two peaks, so far, i'd say.
1945-1950, after the WWII the competitive economies were all in shambles and the US alone accounted for roughly 45% of global economic manufacturing. Until 1948 they alone had nuclear weapons.
1991-2001, after the Cold War and until the disastrous attacks of Al-Qaeda, or rather the disastrous consequences of the attacks. The US was the sole superpower and had immense "soft" power, or cultural power. The way the 9/11 crisis was handled, with the massive budget deficits and the unilateral approach towards international questions made the US lose a lot of "goodwill" and economic power.