Congress, or the legislative branch, of the United States federal government is the primary elected body of the government and therefore their decisions are most directly effected by the populace of the nation.
It makes perfect sense to have the authority that is closest to the people making the decisions that have the most effect on the people. IE: taxes and military behaviors.
America needed new markets for its goods, not a source of raw material for industries.
In concer did you mean concert? becuase if that is what you ment the answer is the war in Crimera just before the first world war.