It's "mom," not "mum." It's "favorite," not "favourite." It's "realize," not "realise." It's "defense," not "defence."
hahahahahahaha
Anyway... here's my breakdown:
70% General American English
20% Yankee
5% Dixie
5% Upper Midwestern
0% Midwestern
California English is actually it's own dialect... but I suppose that it's just incorporated into the "General American English." I went to visit family in Massachusetts during January... and they kept saying that I had an accent... probably because I pronounce the letter "r."