There’s a lot in political science that isn’t certain, and most of it is conjecture. The term superpower is just one example.
There’s an argument for the inclusion of other names. The US is not alone, as its combative stance shows. India is a competitor, and China is now more dominant.
In military terms, the US has chosen principle, and walked a finer line in its diplomacy. The other two haven’t, and still fight over matters the world doesn’t care for.
The idea the UK, France, or Russia, let’s say, can come back from their relative isolation is absurd. All have a Union to be a part of that is stronger than other loyalties.
Yet, this is just the notion of things and is not absolute. If America is due to lose its status it’s not going to leave room for it. The spread of power is always subjective.