Yeah the US only became....
... The US.
Because of the World Wars.
Europe, the then-seat of every worldwide empire, was killing itself and dragging all of Asia and Africa down with them.
The Americas in general were "safe". Isolated from this chaos. Every country in the New World got a boost from the wars.
.... But the US had a nation that was a. Fully Independent b. Relatively Stable and c. Rich in resources -- So they basically got a decade-and-change of time to develop themselves while everyone who had previosly been rich and powerful was getting fucked, and by the time the dust settled, they were the top dogs just because they were lucky.
I honestly think the US and China might be neck and neck
Both are empires Both are very concerned with both their outward image and with what the peasantry is up to, lest they get too antsy.
And both have very advanced technology and a very well developed media ecosystem at their disposal.
They both probably push out about as much propaganda by weight.