Eh -- IMO "empire" is used to highlight an expansionary, hierarchical regime, not just the literal old-school meaning of a single sovereign. Thus "anti-imperial" as it's used today, frequently targeting both post-monarchy Britain and the always-republican USA.
In other words, empires in the day of monarchy were expansive monarchies, and empires in the day of republicanism are expansive republics.
I love how I'm still freaking out but will jump at the chance to argue about pedantics online. It's nice to feel normal, I guess!