Europe in the coming weeks will be facing a host of political and economic challenges that are spooking international investors, endangering American interests and worrying even the most pro-European voices that their historic union has reached its limits in pooling sovereignty and burying historic resentments.

The world is understandably focused on the U.S. political drama circling around President Donald Trump ahead of midterm elections on Nov. 6, and after this week's mercifully failed letter bombs against Trump opponents. The full impact is also not yet known from the Jamal Khashoggi murder story, the focus of my last two columns, after Saudi officials this week conceded the journalist's killing had been premeditated – without saying who ordered it.

Yet for all the significance of those two unfolding stories, the cumulative threats now facing the European Union could be of longer term and greater geopolitical significance. That's because that the same brand of nationalism and populism that unifies Trump's voters, and inflames his detractors at home and abroad, is a far more fundamental challenge to one of history's great experiments, the European integration project that evolved after World War II.

Whatever happens in the United States in November, it's a fair bet that California will remain in the union and that Texas will continue to use the dollar as its currency. However matters unfold in Saudi Arabia, the monarchy itself is likely to survive. In Europe, however, the very nature of the project is in question that ended war, bound the continent together as a growing community of common purpose, prosperity and democracy – 28 countries with a combined GDP of $18.8 trillion.

In the coming days, three stories will take center stage in this drama: in Italy, Great Britain and, possibly of greatest consequence, Germany.