The comparison was with the Pax Romana, which meant peace within the Roman Empire. During much of the Pax Romana, expansionistic war was waged, and throughout it border warfare and skirmishing with barbarian tribes was continuous. Rebellions such as that of Boadicea were also quite common, although seldom very successful.
Applying those same criteria, America has been internally peaceful, with no foreign wars affecting American soil, or directly affecting American citizens, for almost 200 years.
True, we had a major civil war in the middle of this period, but then the Romans had one too. After Nero was murdered, they had three emperors placed on the throne by their troops in a single year, ending with Vespasian on the throne. To be sure, the American Civil War was doubtless a great deal more destructive than this relatively short Roman one. Although the Roman civil wars of the late Republic and of the empire after the Pax were of a scale equivalent in destructiveness to the American WBTS.
During the “Pax Americana,” the US conquered and incorporated the present American Southwest in a major war.
During the “Pax Romana” the Romans conquered and incorporated Morocco, Switzerland, much of Germany, Austria, Hungary, England, Wales, part of Scotland, Thrace, Illyria, Romania, Serbia, Iraq and Armenia, among other areas. With the last two being quickly abandoned as more trouble than they were worth, which modern Americans can sympathize with.
During the course of the Pax Romana, the Romans also converted a great deal of territory from rule by client kingdoms and allies to direct rule by the Emperor.
See my previous examples of two wars fought on all or partially on Amercian Territory.
Every war directly effected American citizens. I guess you didn't live on the coast during the early part of World War II.
I don't have time to correct the rest of your misconceptions.