It's evident that the many Arabic-speaking countries don't constitute a single political entity, haven't done so since a very long time ago, and very likely never will again. Pan-Arabism still exists but as a marginal phenomenon without real influence.
But it's equally evident that there are still linguistic and cultural ties binding them together, since after all their written language remains the same, even if that's a bit artificial and ideologically motivated. They still have a largely shared literature, movie industry, popular music and I might add a remarkable fondness for Eurovision-like TV contests between the different Arab countries in music and poetry. And then there are also some limited political and economic cooperation agreements, such as the Arab League and the GAFTA (Greater Arab Free Trade Area).
None of those things makes them a single nation, or even a closely allied group of nations like the European Union (the Arab League, I think we all agree, is utterly useless); but they do make them a clearly distinct group of nations of the kind that is sometimes described as a 'world', such as 'English-speaking world' or the like. And yes, the majorities in these countries who speak Arabic would describe themselves as 'Arabs' as well as 'Syrians', 'Egyptians' etc., why shouldn't they? Are you seriously claiming that people whose families have spoken Arabic and participated in Arabic culture for centuries shouldn't call themselves Arabs, just because of genetics?
If you stopped trying to make everything so black and white, you'd realize nobody in this thread is calling the Arab world a 'cultural monolith'. There are things they have in common and things that they don't.