Because, first, thanks to England, English has been the lingua franca of business the world over, and has become essentially the universal second language learned around the world which makes communication between diverse peoples possible.
Second, unlike in Europe, most Americans can go several hundred or more miles in any direction, and still not enter a country that doesn't have English as its primary language. In many European countries, a radius of several hundred miles will encounter at least several and in some cases dozens of different languages.
With America and Europe being approximately equivalent in size, what is readily seen is that we all speak the same language, while languages change at borders, and in some countries, there are multiple native languages.
An American can drive from Boston to Los Angeles and not need to know any other language than English. An equivalent drive in Europe, say from St. Petersburg to Lisbon (which is shorter, actually) would entail traveling (depending on route taken) through Russia, Latvia & Lithuania (or Belarus), Poland, Germany (or Germany, Netherlands and Belgium (which has 2 languages)), France, Spain and finally Portugal, with a possibility of a total of 11 different languages.
So, Americans who live in America rarely have any need to even know a foreign language. Most will only encounter Spanish, in Mexico, at resorts where they speak English.
So, stop being a drama-queen ignorant blowhard.