In the 20th century, New England was usually a center for anti-war movements.
Any pacifist tradition in New England is recent and dates from the Vietnam War. Even then, the strong antiwar sentiment was concentrated in lower New England; upper New England has only very recently become pacifist.
In 1940, Irish voters were isolationist and anti-British; they trended Republican. The WASPs felt a certain connection with Great Britain (many had been educated there), and so many of them supported FDR for the first time. Compare the 1940 results in Maine and Vermont with 1948, when the war was over and FDR was gone. They both recorded major GOP swings, as they returned to their normal political state.