Every single person on the planet speaks with an accent; every single person on earth speaks a dialect.
If you look at a map of how dialects spread in the US over time, they all originated on the East Coast, with early immigration patterns directly influencing their development (i.e. Southeastern English in New England, Ulster Scots in Pennsylvania and parts of Virginia, etc.). As the US expanded, these populations fanned out westward and dialects got mixed, diluted, reconstituted, etc. There are very distinct dialects to be found all over the US, but particularly in the West, people aren’t so attuned to their subtleties.
I’ve spent the bulk of my life in Northern California, Oregon, and Washington, which have relatively similar dialect features. Things like upspeak (where statements sound almost like questions…Also prominent in Australian English) and certain vowel raising (e.g. “good” sounding almost like “gid”) frequently appear in my speech. I also do more speaking with a creaky voice (aka “Courtney Love speech”) than most people, and this is thought to be a trait particularly common among young people in the Pacific Northwest.
Linguists frequently like to point out that the idea of TV flattening out everyone’s accent is a myth. In fact, some American accents are actually becoming more distinct, not less. However, there was an interesting study recently by the University of Glasgow that asserted that the spread of “Jockney” (i.e. working-class Glaswegian dialect with some adopted Cockney features) was being influenced by young people watching London-based TV shows. However, I would still argue that TV isn’t the big influence people think it is. People in locations as diverse as California, Illinois, and Michigan have all been polled as stating that people on the national news “speak just like we do”, which is definitely not the case.
I could go on and on about this, as I happen to be doing an MA in linguistics and I’m particularly drawn to issues concerning sociolinguistics, but it’s late. Linguists love dialects and we are at pains to point out that the way someone speaks has no bearing on his or her intelligence: African American Vernacular English (aka “Ebonics”) has very clear grammatical rules, some of which are actually more sophistocated than those of Standard American English, they just happen to be different rules. The same could be said about the dialects of people from South Boston, the Blue Mountains, or Hawaii. Unfortunately, in the quest for greater economic prosperity, most people don’t seem to be so enlightened. In a study from the 1970s of English in New York City, a group of business leaders were selected to listen to random samples of New Yorkers and assess what jobs they were qualified for based on the way they talked. When one woman spoke a short sample including 10 examples of the letter “R”, she was given a score of 70 % likelyhood of getting a well-paying secretarial job. Later, the same woman’s voice appeared again reading the same sample, but this time not pronouncing one of the Rs. Her score plunged to 35%.