This is a question has been bothering me as someone who’s country was colonized by the British Empire. We were taught about it in schools and how it lost power over time but never how the USA came to take its place especially over such a short compared to the British Empire.
I don’t want to go into a big long thesis so I’ll try to summize.
America, now firmly cemented in its boarders, fully federalised and with a wealth of natural resources and ballooning population was becoming a big power by the start of the 20th century and American politicians were putting in considerable effort into undermining the big European powers, but especially Britain.
The British empire being so spread out made it hard to defend and control. So with Britain and it’s colonies fighting on every front for the whole length of the war Britain lost many colonial holdings in Asia.
Those colonies also paid a heavy price in the fighting and independent movements flourished after the war and Britain didn’t have the money or political will the fight them, so the empire dissolved.
America was able to use its war economy to massively ramp up its domestic manufacturing.
They were also able to use their position as financers and occupiers in Europe and Asia to extend considerable American influence to those regions. And also Latin America and the Caribbean. Giving American companies influence over much of the world without the obligations the British Empire had.