America was feeding The Allied effort with thanks and naval vessels...I do not think FDR wanted war, I think he wanted to get the USA of the muck that was the Great Depression.
It increased trade of iron with Allied countries and provided financial aid as well. But it didn't provide tanks or navy as far as I am aware.
While the USA economy benefitted tremendously from the war, I don't think anyone could have foreseen that, and no President would attempt to improve an economy by increasing financial aid to foreign countries.
One of the figures I read was £80 billion, that America had given to Allied powers by the end of the war!