The possibility that our known history of ancient Rome may be a fabrication is almost too fantastic to contemplate. And yet I wouldn’t be altogether surprised.
The practical problems of verifiable chronology are acute, and archeology as it stands today offers only a spotty and contentious record to measure recorded history by. No one, for example, can state with certainty how old the Sphinx might be or when Stonehenge was originally constructed and by whom. Or, it would seem, whether a man named Julius Caesar ever conquered Gaul.
Imagine the conspiracy! Nations define themselves by their histories, making the ability to shape history the ability to produce the perfect propaganda. It would not have been hard for a secretive cabal of scholars, living off the patronage of princes in an age before printing to manufacture national identities in the name of good government.
Speculation, yes. Whether grounded or not depends of what we actually know with certainty about the ancient world.