Though people from different geographical areas and ethnic groups settled in America, there is a uniformity in American English . The reasons for this uniformity have been discussed below.
Traditionally American is called a Salad Bowl and the most prominent characteristic of the occupation of the United States is the constant mingling of settlers from one part with settlers from other parts. Not only the English settlers, but also the French and German settlers also have this tendency. Thus colonists from Massachusetts went north into Maine and New Hampshire and south into Rhode Island and Connecticut. Others moved from New England into New York, New Jersey, and colonies as far south as Georgia, as when a body from Dorchester in Massachusetts, known as the Dorchester Society, moved to Georgia in 1752.
Thus, due to this admixture of peoples the American society has become highly homogeneous. Linguistically the circumstances under which the American population spread over the country have had one important consequence in the fact that the English spoken in America shows a high degree of uniformity. Those who are familiar with the pronounced dialectal differences that mark the popular speech of different parts of England will know that there is nothing comparable to these differences in the United States. Thus, being much more unsettled, and moving frequently from place to place, the Americans are not so liable to local peculiarities either in accent or phraseology.
The merging of regional differences through the mixture of the population that has been described has been promoted since by a certain mobility that characterizes the American people. It has been said that it is unusual to find adult Americans living in the place in which they were born, and while this is an obvious exaggeration, it is nevertheless true that change of abode is distinctly common. Americans are so accustomed to distance that they disregard it. So, the Americans share a feeling that tends to create an attitude of mind that may almost be said to diminish space.
The Americans share an instinct of conformity and the fact that they readily accept standardization in linguistic matters as in houses, automobiles, and other things.
Another factor that helped the American English gain a uniformity is the influence of Webster. Americans respect in language the authority of those who are supposed to know it. So, the language of the Americans was influenced by Webster’s spelling book and Lindley Murray’s grammar. The public education in America has been a constant influence in the uniformity of the American English.
It is true that like any major language of the world American English also has some variations. There are at least nine varieties of American English which have enough coherence within themselves and distinction from other varieties, to warrant their description as separate dialects. But the variations are so negligible that the speakers of any dialect can easily understand the dialect of other groups. Thus, compared to the situation in European countries, such as France or Italy or even England, dialect differences in American English are relatively small.
A History of the English Language. Baugh, Albert C., and Thomas Cable. 4th ed. Englewood Cliffs, New Jersey: Prentice Hall, 1993.