An English friend of mine likes to say, "America and England, two countries seperated by a common language."
I did misspeak earlier about the joining of States. Hawaii was a horrible blot on America's history. The territories taken from Mexico as well. Even though Mexico "started" it, Polk's activities were designed to provoke the attack.
I have to agree with knowltok2 though that the original spanish population is a very small percentage of the current Spanish speakers in the US.
That said, many of the posters from various countries that are against the US having an official language have, in fact, official languages in their countries. While some of them have two languages, it doesn't necissarily take into account any influx of immigrants that speak other languages. The following link is a breakdown of languages spoken in Canada.
http://www.statcan.ca/english/Pgdb/People/Population/demo18a.htm
Is Canada planning on adding additional "Official Languages"?
Are other countries that have significant immigrant populations and an official language planning on adding other languages?
http://www.ethnologue.com/show_country.asp?name=Finland
http://www.ethnologue.com/show_country.asp?name=USA
Finland is a case where it's bilinguagal official languages do pretty well cover its population. Only minor populations speak only non-official languages. Also, in 1992 they added to their laws that the sami population can deal with authorities in their native languages- which normally involves having translators present. This was added to help preserve the native culture. Samis are what in older times was meant when someone said "a Finn" from my brief research. It seems calling someone "a Finn" is derogatory now.
The USA has a lot of native languages. Effort should be made to try to keep most of them alive. Some just don't have the population left to be a feasible though. Having an official language would not help nor harm that goal though. What impacts the native languages is whether the speakers stay grouped and whether it is a written language. Not something that can be solved by laws. But improving living conditions on reservations would go a long ways.
From my perspective though, the only thing make English the official language in the US would accomplish is to codify what already exists. Businesses would continue doing as they do to please their customers. People would continue to speak to each other in whatever language they are comfortable. Government would still issue its edicts in English, post it's road signs in English, etc. And minority media would translate the edists into their languages. If too small of a minority, you won't have any translation available and will remain ignorant of what the government and the rest of the US is doing.
The US would be a tower of babel if a language was not the defacto standard, what is the harm in codifying it?