By Trevor Hunnicutt, Steve Holland and Mike Stone WASHINGTON (Reuters) -President Joe Biden pleaded with Republicans on Wednesday for a fresh infusion of military aid for Ukraine, warning that a victory for Russia over Ukraine would leave Moscow in position to attack NATO allies and could draw U.S. troops into a war. Biden spoke as the United States planned to announce $175 million in additional Ukraine aid from its dwindling supply of money for Kyiv. He signaled a willingness to make significant changes to U.S. migration policy along the border with Mexico to try to draw Republican support. “…