In large geographic areas that speak the same language, there will always be differences between locations that are distant from each other. You see this effect all over Europe, more so because of the many borders where languages can intertwine more, but it still happens in the US. You can see differences between Northern and Southern California because of this. You can see the same types of differences in other parts of the east coast, Texas, the midwest, etc. Accents and idioms are all slightly different.