If successful, Congress would only be able to disapprove of war, which turns the Constitution on its head! Furthermore, any resolution of disapproval could be vetoed by the President, meaning that two thirds of Congress would need to disapprove of a war, rather than a majority to approve of one, as the Constitution states.
"The Congress shall have Power To . . . provide for the common Defence and general Welfare of the United States."
—U.S. Constitution, Article I, section 8, clause 1
Like many powers articulated in the U.S. Constitution, Congress' authority to declare war was revolutionary in its design, as the founders saw the atrocities carried out by centralized heads of states like kings and queens and set out to prevent them. The Constitution was a clear break from the past when a handful of European monarchs controlled the continent's ability to tax, make law, and wage war.