A lot more adult of a superpower than say, China's petulant behavior. The US is a mostly benign superpower in comparison. People like to say the US is violent and imperialist and what not, but it's a lot less so and a lot more benevolent than any prior superpower has been in past centuries. Ignoring the past and looking at the future, just look at how China is going all gung ho at the silliest perceived slight, going into petty trade wars with major trading partners over the silliest things (Australia inquiries into the origin of COVID).

So realistically, there's not a lot of "maturity" on the geopolitical world stage. The US is objectively on the "adult" spectrum.