Paul Kennedy is Dilworth Professor of History and director of International Security Studies at Yale University. His books include “The Rise and Fall of The Great Powers,” and, most recently, “Engineers of Victory.”

So President Obama won’t have a one-on-one conference with his Russian equivalent, Vladimir Putin, at the time of the G-20 meeting in Moscow, partly because of a nondescript “leaker,” Edward Snowden — that is not good. So Chinese public opinion (however that is cooked up) seems to be ever more nationalistic these days, while Japan launches its first aircraft carrier since the Pacific War — surely also not good.

So America’s National Security Agency looks as if it is spying on everyone, domestic and foreign, producing bouts of outrage — that is a bad business. So the European Union is as divided, confused, angry and leaderless as, say, the former Holy Roman Empire — this is surely not good. There’s more: Argentina is huffing and puffing about the Falklands, and Spain is huffing and puffing about Gibraltar. Not good at all.

To historians of world affairs, including this one, the only proper response to this litany of spats, pouting and injured pride is to ask: “Is that all?” Are these the only issues which divide and upset the Great Powers as we enjoy the second decade of the 21st century? And, if so, shouldn’t we count ourselves lucky?...