Culturally and even ethnically speaking Egyptians share more in common with Greeks and Italians that their fellow African brothers. The same can be said for Tunisia and Turkey, Syria in Asia.
Historically it makes sense to group them together but most do not. Is it because of religion or politics in general?
I asked the same question to a friend and he said it was geography but if that was the case wouldn't we group Europe with Asia? And even Africa and Asia have a land border. So if anyone would enlighten me I would be grateful.
A few years ago one fairly eminent world historian (who hasn't come out with his book yet, so I won't out him) started to promote the idea of "Indo-Mediterranea," to recognize that in the ancient, medieval, and Early Modern eras, there's been tremendous linkage (trade, culture, conflict) between and within those areas all the way from India to Iberia and Ceuta, in kind of a tuning-fork shape.
The reason for mentioning this is because "Indo-Mediterranea," like Europe, Africa, or Eurasia (or various regionalities) are all metageographies. Using any of them serves to create certain subconscious linkages (and sometimes conscious ones). Lewis and Wigen's The Myth of Continents: A Critique of Metageography (1997) is very good and readable about these points.
I'd argue that no, you can't consider the nations of North Africa and the Middle East (or SW Asia, or whatever you prefer) to be part of Europe, because then it's not "Europe" as we usually understand it--it's the Mediterranean world, or the Euro-Mediterranean, or something else. It also depends on when in history you're talking about. If you're dealing with the pre-New Kingdom era in Egypt, "African" makes as much sense as anything else.
Generally speaking, the Western World has not viewed Islamic civilization as drawing from the same Greco-Roman tradition as themselves. Due to the of cultural exchange in the Mediterranean Sea including centuries of Greek, Roman and modern western imperialism( Most North African states were still colonies post-WW2 and fought wars to be free of western dominion) rule of the near east and conversely Ottoman and Islamic rule in southern Europe drawing such east/west boundaries is highly problematic. Despite this, the traditional narrative would imply that centuries of cultural contact with the east, beginning with colonization of the North Africa by the Phoenicians, but most decisively with the Islamic conquests and the increased cultural separation as well as mutual antagonism towards a religious other is why North Africa tends to be viewed as being separate from Europe.
I also think that understanding modern day immigration and the resulting cultural tension with North Africans in Europe are also going to play a role in any answer to this question, but I am not informed enough on that issue to comment
You shouldn't assume that there is rhyme or reason to these kinds of decisions. Nor should you expect them to be consistent.
They really shouldn't be considered part of Europe, that's more of a geographic designation. You're right that Asia and Europe do not have a geographical border that is as significant as the demarcations between the other continents. But that's more of the exception to the rule than anything else.
You're also right that in a lot of ways North Africa is certainly more in common with the Middle East than it is with the rest of Africa. That's primarily because of the significance of the Sahara in limiting cultural diffusion. In certain circles, people use the blanket term "Middle East and North Africa" to refer to that cultural zone.
Diversity within a continent is often very large. Think India vs China (again, major geographic barrier of the the Himalayas).
To summarize, I wouldn't put too much value in continents as a way of clustering culture.