First of all, the USA has the indigenous populations of Cherokee, Navajo, Hopi, Sioux, Creek, Iroquois, Cree, Blackfoot, Seminole, Ute, Apache, Paiute, Yaqui and many others, all with their own native languages and I think you get the point.
The colonization of the British on the Eastern Seaboard brought the English language to the area that will become the USA . American expansion furthered the language to new lands in the West and various American English dialects and regionalisms were added to the English language.
Of course there are areas of other European languages that are commonly heard in multicultural USA. Let's say the world split into two spheres, the Western and Eastern Hemispheres and there wouldn't be any contact between the two. The European languages in the Western Hemisphere may have evolved further from the Eastern mother tongues hence why we have a myriad of tongues, some related such as the Romance languages (Spanish, French, Italian, Portuguese) and Germanic languages ( German, English, Dutch, Swedish) but as an English-speaker, do you understand German or Dutch?
Many centuries ago, rivers, mountains and deserts were formidable barriers. A example was Latin which was spoken throughout the Roman Empire.The Roman colonists in present-day France, Spain and Italy all spoke Latin. When Rome fell, contact ended and Latin in these various areas evolved to their present languages. With the former colonies of Britain,now known as the United States of America, trade and commerce continued; therefore, English remained the language of the new fledgling Republic in order to easily communicate with the English seller and the American buyer, and in time the American seller and the English buyer. Britain and the USA, from the beginning have had a lot of interaction, both culturally and economically.
So I wouldn't base my opinion whether a country is "great and powerful" solely on a language, especially a fairly new one when compared with the ancient countries of the Old World and which was colonized by other nations, but is now as an independent nation and don't forget the instrumental role the USA played by making English a great and powerful international language.