A lot it seems. First off, not all immigrants, illegal or otherwise, learn English.
Barry Obama would know this if he spent some more time in California during his 57 state tour. I remember seeing an article in a Contra Costa County newspaper last year were a 20 year resident of the county was interviewed, and the reporter had to use a translator, because the woman being interviewed couldn't speak English!
Governor Schwarzenegger was serious when he told those in his state who use Spanish as their primary, and often only, language, to put down the Spanish language newspaper, turn off the Spanish language TV station and learn English.
If had done any traveling in Europe, he would know that English is taught in their schools because it is considered valuable in the workplace. I was at one multinational corporate engineering center in Europe where the staff was from Norway, Sweden, Germany, France, Holland, Poland, and a couple of other smaller countries. The common language they spoke at work was English. Not German, or French or Spanish. As Swede told me when I was in Stockholm, "We like to travel. Nobody speaks Swedish. So we learn English and we can travel pretty much anywhere."
Being multilingual is nice, I've studied Spanish and German in the past, but International business is mostly conducted in English. If I had to pick a second language to assist America in the World Market, it wouldn't be Spanish. Mandarin, Japanese or German would be better picks.
Update: Unlike Senator John McCain, Barak H. Obama does not speak Spanish.