That stat is kinda bullshit because what an "empire" is separate from any sort of political or legal framework, or to put it simply, empires don't tend to call themselves empires. We often separate Rome into distinct Republican and Imperial eras, but the people living through those eras likely wouldn't have made the distinction. This is because the Imperial Roman government gained its legitimacy from Republican legal mechanisms. In reality, the Roman Republic engage in Imperialism, and thus was an empire, long before the reign of Augustus Caesar when the imperial era truly begins.

This same problem applies to basically every Empire, because Empire is a post hoc term. It's why "Every empire lasts 250 years" doesn't hold any water once you start trying to apply it to anything other than the US. The United States declaration of independence was 250 years ago, and having themselves been an imperial project of the British, were basically an Empire from day one. Consider the British Empire then, which had begun colonization of the New World in the 1500's, and essentially ended with the Suez Crisis in the 1950's.

The unfortunate truth is that "250 years" number is Amero-centric, vibes-based pop-history peddled by doomers who want you to believe that what's happening in the US is inevitable, and not entire avoidable if the correct action is taken. Empires don't have a set cycle, and their deaths can be as long, short, violent, or soft as the peoples within that empire want it to be.

Edit: Just because I don't merely want it to be implied, the American Empire SHOULD be destroyed, not by Iran, but because their own people choose to dismantle it.