HELSINKI — Hours before meeting Russian President Vladimir Putin one-on-one for a high-stakes summit here Monday, President Trump echoed Moscow’s view by saying the United States — not Russia — was to blame for hostilities between their countries. Although most U.S. officials argue Russia’s interference in the 2016 U.S. presidential election, use of a nerve agent on British soil and aggression in Ukraine and Syria have worsened relations, Trump instead faulted “U.S.