Certainly the US was an SP by the end of WW I? Yes?
Even before. That’s why the Spaniards knew their empire was at the end when American ships sailed to Manila Bay built with steel while the Spaniards still had wooden galleons. Surrendered the Philippines at that instant and they knew who was the new boss on the block.
In read some histories on WW1 I read where a lot of stuff we used was borrowed from the French. We really didn’t gear up until mid-1918 and by then Germany was on the ropes so to speak even though they had a few offenses that caused the Allies some worry.
The US became a superpower when it put 3,000,000 men in the field for the Civil War.
It expanded that status with the US Naval victories in the Spanish-American war.
When Pershing won the Battle of Saint-Mihiel on the strength of the US First Army (500,000 men) in 1918, there was no looking back.
In total the US put 2,000,000 combatants in France by 1918. Nobody had ever put that large an Army that far from home before...unless they walked.