President Joe Biden's apparent call for Vladimir Putin's exit reverberated instantly around the world, sparking an administration rush to course-correct -- and risks scrambling US efforts to rally a united front on the Ukraine conflict. Biden's comment that the Russian president "cannot remain in power" -- delivered in Warsaw at the close of three days of marathon diplomacy -- was termed "a horrendous gaffe" by one Republican senator. A senior US analyst said it could have the effect of lengthening the war. And even France's president warned such language could "escalate" a conflict the United States and its NATO allies...