Oy vey...
I am sorry, but you ust managed to trigger a whole set of memes that site members generally use humorously. PLease brace for impact.
To adress the question: Need More data. You would first have to define what you mean by the 'Dark Ages' and why and how they do not happen. If I were to posit, frex, that Greek and Carthaginian civilisation are destroyed by the Celtic migration and that Europe subsequently developed a largely illiterate culture, that would be one way of avoiding the 'Dark Ages' of 500-700, but probably not what you had in mind.
Regardless of what definition and point of departure from our history (POD) you adopt, the United states is very unlikely to exist. Its foundation is dependent on so many things that even a much less significant change would render it unlikely. Without the Dark Ages, there wouldn't be English, let alone England, so no chance of a USA.
As to the question of acelerated technological development in a surviving Greco-Roman world, we have a tradition of dragging out that debate every few months. Usually, the POD is something to do with the Library at Alexandria. If you're lucky, you can have the distinction of your post being the occasion to rekindle it.
If you're a sockpuppet - good satire.