Sorry, meant that now deleted reply for someone else.

Two words: Armenian genocide

Yes, they were a regional hegemon.

If I'm being generous, from the view of the average Roman citizen, they were a global hegemony, because they didn't know how big the world really was.

But they were not. There was no shortage of rival empires, some even right on their borders, and all during Pax Romana, including the Parthian Empire, Kushan Empire, and the Han Dynasty.

And my history is a bit rusty, but I'm pretty sure Rome tried multiple times to conquer the Parthian Empire, and failed.

Most importantly however, their reach did not extend across the globe, only where they could build their roads through, or sail their boats to, such as Carthage.

Also, Pax Romana, refers to a period of relative peace for Rome, brought by their imperial power. It's only indirectly related to their hegemonic status, but it's not in reference to it.

You're confusing hegemon and classical empire, with global homogeny. We can debate whether or not global hegemony is unique to a unipolar world, but I don't think it's very debatable that it's only been achieved through the use of neo-imperialism.

That is to say, no classical empire has ever achieved truely global hegemonic status, but there's no shortage of historical hegemonic powers and classical empires, including that European ones you listed.

I will say that while I generally view the British empire as a classical empire, it's competition with other European powers in the 19th and 20th centuries is what really gave rise to the concept of neo-imperialism.

But the Monroe doctrine put real checks on their imperial power and influence, that they could not, or would not, overcome. Which is why I have a hard time considering them a global hedgemon in the same context as America, but I realize for their time, they could be considered the first global hegemon.