Before that American leftists were going to Spain to fight against the reactionary rightists as they called Franco's regime and their German and Italian allies.
You can't call Hitler a socialist and then ignore the nationalist part. Mussolini created this blending of right wing and left wing with his fascisim mishmash.
OK but a National Socialist is still a socialist. The only real difference between the Nazi version and the communist version is who has nominal title to the means of production. No differance at all when it comes to who controls things, or with regard to individual rights. You will note that when Hitler attacked the Soviet Union, it suddenly became Mother Russian, so there was signifigent streak of nationalism there as well.