Not true, I know many 3rd and 4th generation Greeks here who speak fluent Greek.
Lets face it, many immigrants who come here at an advanced age 30+ have a very hard time picking up the language, its just more difficult to do then when you are younger but i'm willing to bet that the majority of immigrants who come here know that they have to learn some English and try and have some success albeit broken.
This must learn English and English as the official language crap is a joke, its just red meat for the base that has zero effect on any perceived immigration problem.
Anyway i'd like to see some of you guys move to lets say, Russia, and be speaking decent even within 5 years. Wouldn't happen. Hell many Americans won't even bother to learn basic shit like hello and goodbye when on vacation in a foriegn country, we just expect everyboody should be able to speak English.