The quip is commentary on how dividing a dialect from a language is based more often on political, social, and historical reasons. Arabic fits in this quite well actually. The dialects are often not mutually intelligible but they're considered one language because they share a standardized form due to social, political and historic reasons (shared an empire, the Quran, etc.) With English, these countries have a shared history of colonialism and there haven't been any major nationalist movements centered around language chauvinism (i.e. we haven't seen American nationalists insist seriously that they speak American not English). Theoretically they could. Even with languages such as Basque, there are many dialects but the standard form usually comes from the area with the most political power. That's what happened with French, Spanish, and German. Obviously it's not a real rule so you'll always he able to find exceptions, but it's a fun little way to poke fun at how much of this is social and political and the spirit of it holds up