By Elizabeth Dilts Marshall NEW YORK (Reuters) – Global stock markets rallied in Europe and North America on Wednesday after three straight days of selling, and oil prices retreated from the peaks scaled over the last week as investors digested the news of Russian oil import bans. Moscow accused the United States on Wednesday of declaring an economic war on Russia, and said it was considering a response to the U.S. ban on Russian oil and energy imports. Russia’s economy faces the gravest crisis since the 1991 fall of the Soviet Union after Western nations imposed sanctions on Russian companies…