Diplomatic efforts to avert a Russian invasion of Ukraine have failed to ease tensions — and  that has huge stakes for Ukraine, for Europe and for America’s standing in the world.Read more:The U.S. State Department has announced that the U.S. will close its embassy in Ukraine’s capital, with remaining embassy personnel being relocated closer to the border with Poland because of mounting U.S. fears of an invasion by Russia.Russian President Vladimir Putin appeared to leave the diplomatic door open, but as national security reporter Shane Harris explains, talks aren’t producing any breakthroughs.