My guess is North Dakota would have been the most isolationist given its dominant Scandinavian/German demographic (highest Harding vote, Lemke vote in 1936 etc.), with Wisconsin next.
Most interventionist is harder.
Of course the social base of isolationism differed between WWI and WWII. New York for example would have been more interventionist re WWII compared to WWI...
The most interventionist states during the World Wars would have to have been the
Upper South Atlantic states comprising North Carolina, Virginia, (parts of) Maryland and Delaware. North Carolina showed only a very small swing to the GOP in 1920, and actually swung to FDR against Willkie in 1940. Cox obtained 56.69 percent there in 1920, whereas Wilson who won 15.13 percent more nationally only won 1.41 percent more in North Carolina. In Virginia, Cox lost only 4.99 percent, and in Delaware only 5.16 percent.
In 1940, these trends repeated very strongly. Willkie remains the only Republican to lose Davie County, North Carolina since 1916, and the first to lose Calvert County, Maryland since 1880. The Southwest (Colin Woodard’s “El Norte”) was also highly interventionist.
In both cases, these reflect the fact that semi-feudal social structures meant Southern and Eastern European migrants were (apart from Maryland) practically non-existent in these states, and with the Southwest, fear that nonintervention would lessen or eliminate American control over Latin America. There is a contradiction in the highly interventionist character of these states given their pervasive racial discrimination against not only blacks, but also Native Americans and Mexican Americans. Politically these groups were entirely or almost entirely disfranchised until the 1960s by a combination of statuatory laws, literacy tests and poll taxes – creating a social structure much closer to the racial hierarchies of the Nazis than their more egalitarian battlefield enemies.
In contrast, upper New England was interventionist and logically so because of its strongly English (or French) population and strong democratic traditions.