US Senate Majority Leader Chuck Schumer attends a press conference in Lviv, Ukraine, on February 23. Roman Baluk/ReutersUS Senate Majority Leader Chuck Schumer issued a warning Sunday about the need to supply more aid to Ukraine and vowed not to “abandon” the European ally.Speaking after returning from a trip to Ukraine, Schumer said this year is a “crucial moment in the history of the world,” adding that a Ukrainian loss to Russia would also be “devastating in consequences for the US.”“This is a turning point, an inflection point as to the United States’ ability to project itself —…