Did the USA ever experience “Pax Romana” like ancient Rome did?
Probably not. Pax Romana, as I understand it, was a lengthy period of time where Rome had relative peace and little expansion . . . this probably due to to the empire already being fairly large. As the US, contrary to what many believe, is not an expansionist empire (the westward expansion could be argued, but I digress) and therefore there was really little to do in the expansion department. The peace side of things is where things don’t necessarily indicate Pax Romana-like qualities. Though there have been relatively few wars, military action of varying degrees has been more or less going on from the beginning . . . whether that be in response to piracy during the early years of the republic or protection of American interests in various and sundry areas of the globe.