You're not going to have a 'National Socialist American Workers Party', though, because of the electoral system in the United States. *Hitler is going to have to work his way up through one of the major political parties, which means he'll either be a Democrat or a Republican.
German immigrants tended to be Republican, though Hitler's family background is Catholic, which throws a wrench in the former, with the Republicans denouncing the Democrats as the party of 'Rum, Romanism, and Rebellion' since after the Civil War. Anti-semitism in the United States also isn't going to be as strong as in Germany, which has a history of anti-semitism, as well. Your ALT holocaust could be against African-Americans, though, and Hitler would probably have firm support among some Southern politicians for a eugenics/'depopulation' program for the black population.
