The Decline of British English, Visualized
While British English may rightfully claim the honor (honour?) of having anteceded its American cousin, there is no doubt that today American English is the defacto English in the world. Below are a few charts generated using Google Ngram Viewer that show the decline of the frequency of British English and the rise of American English in its stead.
Note: American spelling is in blue, while British is in red.
Gray vs. Grey
One of the early signs of the rise of American English can be seen in the prevalence of the American "gray" over the traditional "grey."
Flavor vs. Flavour
Further evidence of the ascent of American English after 1880 is visible in the increasing frequency of "flavor" in English-language publications.
Liter vs. Litre
Despite the metric system never having been accepted by the majority of Americans as a standard unit of measure at the turn of the 19th century, the American spelling of the units of volume gained wider popularity than did the British version.
Center vs. Centre
1913 marked a turning point in the usage of the British spelling, as the American alternative became more frequently used in literature. This was just a year before the beginning of World War I, which many view as a key period in America's rise to superpower status.
Defense vs. Defence
World War I also coincided with the growing usage of the American term as the nation's stature in the world increased.
Airplane vs. Aeroplane
After World War I drew to a close, the American term overtook its British counterpart in frequency of use in literature.
Fiber vs. Fibre
At around the same time, the world "fiber" was quickly becoming more popular than its predecessor.
Honor vs. Honour
Despite having lost their lead in most terms, the British can take pride in mounting an impressively long defense of "honour." The American spelling only managed to solidify its lead in the 70s. Interestingly, the word's frequency has dropped off significantly in the past two centuries.
Jail vs. Gaol
If there were ever a word that failed to make it across the Atlantic, it must be "gaol." Ever since the middle of the 19th century it has been fading into obscurity as even the British Isles slowly rejected the old spelling.