I would point out two significant differences between the US even as you emphasize what you perceive as similiarities:
1. US power is part of a larger consolidation of power and redistribution of resources known as colonialism. It is embedded in worldwide fascism, brutality, genocide: murders of hundreds of millions of brown, black, and indigenous peoples with a subsequent redistribution of wide range of these resources, worldwide, from about 90% of the human race to about 10% (European/white).
Because this MASSIVE shift in resources which enriched Europeans at the expense of pretty much everybody else required so much effort, it required a UNIQUE invention which would exert control and dominance worldwide.
This invention is called WHITE SUPREMACY. The Romans didn't have it: they had what dominant countries have had for as long as the human race has documented its existence: local dominance with attempts to spread outwards, but NEVER the actual 'success' in this arena.
US dominance has required that particular invention.
The invention of WHITE SUPREMACY distinguishes the US from the Roman Empire as well as every other empire that has ever existed; none have required an invention that would put a heavy foot on everybody else's neck by casting one of those groups (Black) as fundamentally inferior/opposite and everyone else as somewhere in between (but still 'subhuman'). Without exploring this significant difference, we won't understand why this sort of fascism is cloaked in false decency.
2. US dominance is worldwide: white supremacy has damaged hundreds of millions of brown/black/indigenous peoples--many of whom may have had the potential to cure cancer, diseases, etc, etce etc---and handed those resources to Europeans who have passed them down for generations.
No other empire has EVER damaged everybody else, in the Gestalt, prior to the US's (and Europe's, to some extent) both gross and minute poaching of resources, which Europeans/Americans still hold in the form of inheritances, etc.
The Roman Empire may have damaged a lot of people locally with some extension, but it would be less than the far-reaching worldwide consequences of jeopardizing ALL non-Europeans (with the exception of Russians) through stealing of necessary resources.
Decline in 'patriotism' is not really a decline in patriotism unless you believe that the US is for European peoples. The decline in patriotism is an exposure of the high-grade denial and shirking of fundamental human morality that this group of people needed to adopt in order to exact such extreme crimes, including extermination of millions of non-Europeans, and not feel the profound deterioration of morality that this actually represents.
What you call 'decline in patriotism' is actually a revelation of criminal behaviors that have yet to be acknowledged, in any sort of comprehensive fashion, by the people who still benefit from the historical--and current--behaviors which still determine not just their unjust enrichment but also the continued denigration of most other human beings, in the Gestalt.
Let me put it succinctly: if one group spends 500 years murdering many other peoples and then stealing their stuff, expect those many other peoples to be angry and, at some point, to try to get their resources back. That's true whether one is in the US, where Black and Indigenous peoples are still at a massive disadvantage, and at many other countries still suffering from centuries of poaching and colonialism. We are only postcolonial in the sense that European countries have officially left; the impact of their deleterious behaviors is still present in virtually every country from which resources were poached.
There's no patriotism in claiming you have a republic but then behaving as if you have a fascist state meant only to protect one group of peoples and which has done so at the expense of a wide range of others worldwide, and to and extreme, Black and Indigenous peoples in the US.
Is it really 'patriotic' to defend fascism that keeps a heavy boot on our necks just so one small group (c10% human race) can continue to keep all those stolen resources??