Today in existential threats

What's the existential threat weighing on the minds of Col. McCormick and his enterprising stable of cartoonists on June 30, 1941? 

The hanky that "enterprising widow" Europe is waving is labeled "Union Now" -- the roughly two-year-old "federal union" movement for a transatlantic state (or, as the Tribune put it a day earlier, "the scheme for an immediate union of the United States and the six still-free democracies of the British commonwealth of nations"). This, as you can imagine, was not the Trib's idea of preserving the exceptional American way of life.  I mean, just look at Europe's little friends there.