Rome wasn't the most powerful empire, merely the third longest lasting; the Assyrians and Egyptians had a run that puts Rome to shame, and the Khans wielded far more power than any individual emperor.

The US is just the only world power left in modern time that could deploy anywhere within 24 hrs with more than just a strike force (and they can do so far far harder than any previous "empire"). The US "empire" is based on deployment potential, banking, and diplomacy. Nukes are just the key required to gain entry to the table so you don't get wiped at deployment.

Bricks is literally the alliance trying to match US power and still hasn't. This is mostly a barrier to entry problem rather than personal power, but it does stand that no previous empire could match the modern US in millitary, finance, or diplomacy.

But hey give it 50 years we are doing our best to shit on two of those.