About half of the countries in the world do not have an official language, such as America, such as Australia, to which English and its particular local dialect modifications exist as the de facto language of the country, but is not in fact by law the official language of the country, in contrast to countries such as France and Spain that do have an official language, which obviously respectively is French and Spanish. Perhaps it is questionable as to whether the United States needs an official national language, as the country seems to operate just fine without it, but this doesn't mean that it couldn't run better, or be better off, with an official language.
In fact, 31 of our 50 States have declared English as the official language of their respective States. The primary reason that they have done so is so that the population as a whole will more easily and more readily assimilate English as the language of choice and subsequently be able to communicate better and for all thereby to better understands each other. Declaring English as the official language of an individual State doesn't mean that somehow other languages are outlawed; instead it means that the State apparatus may conduct its business in the language of English, as opposed to being compelled by law to furnish materials in languages other than English. Of course, in America, it has already been adjudicated that Federal law trumps over State Law, so for Federal regulations, States would still be under Federal law language requirements.
The language used most often after English in America is Spanish. While it is understandable that people that know only Spanish, or come from a Spanish heritage, would prefer to speak and to read, in their pleasure as well as in their work, and to conduct overall their life in Spanish, that does little or nothing to properly assimilate these residents into the very fabric of American life. Language is the way that we communicate with each other, and it is important for a united country to be able to communicate effectively. Additionally, there should never be two countries within a nation, or three, or even more, we should all be one country, united, under one flag and with one purpose.
In truth, we do our fellow citizens a grand disservice when we permit, aid and abet them, and encourage them to speak in a language that is not the true de facto language of choice in America. We should instead do everything that we can to see that instead of living within a nation on self-imposed language-created crutches, as they strain to understand English, or, much worse, ignore English as a language, that they are instead given the opportunity to learn and to excel in English through tools and programs that are specifically built around accomplishing these worthy goals.
The United States is still a nation with prejudices, and with quick judgments, to which it would far better serve residents of this great country, to put forth the effort to become proficient in English so as to put a sword through the lie that they aren't "real" Americans. This country needs more bi-lingual people, because America is the international leader in commerce, and believes itself to be first in peace and desires greatly to be the beacon of light of freedom for all peoples to aspire to in this world, no matter their creed, color, sex, or preferred language.
While it may not be necessary to make English the official language of these United States, this country knows the virtue of literacy for all which makes for a greater nation of people knowledgeable in their own affairs, knowing English should also be part of that firm foundation that strengthens the ties that bind us into one nation, whole and indivisible.