The "normal" American accent is a sort of midwestern accent (but without any Iowan accent) - kind of like Chicago. ('m not saying that from a biased viewpoint - I was born and raised in New York City, and my accent is so noticeable that I've been asked if I'm from NY when I've been overseas in non-English-speaking countries. Hearing an accent in a foreign language means it's pretty strong. [Hearing a recording of myself, I have an accent to my own ears.])
But yes, to a speech-to-text program that hasn't been trained, we all have accents. (Dragon Naturally Speaking takes a while to train, but then it's almost like a little administrative assistant - a doctor of mine used it to take notes, and he had it trained so well that it got the spellings of medical terminology right. But they don't make DNS for cellphones.)