http://www.washingtonsblog.com/2015/02/america-war-93-time-2...
I think, to be meaningful, Pax Americana must refer to an "empire" larger than the territory of the United States. There hasn't been a war in Western Europe since 1945; the longest lasting war in South America was the Falklands War at 74 days.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC65039/
When peace lulls, there is no social change.
So I would say that there may not be wars fought with swords and cannons as much as olden days..but it's still being fought over land, ideology, water and resources.
I think Pinker has done his earlier fans a disservice by transforming into someone I certainly don't recognize but I am not all broken up about it because I have disowned Richard Dawkins too and that had prepared me. Maybe that's why he is calling himself an 'experimental psychologist' now instead of the cognitive scientist, linguist and psychologist he used to be..