Article 5 is an interesting article that had only been invoked in NATO once, in 2001, too recently to discuss here. Suffice to say there is no cold war example we can use to demonstrate how this article could have worked.

Although not specifically stated, the collective defence clause is widely understood to mean attacks by external forces outside the country. In order to invoke the article, France would need to invoke the article in a meeting of the North Atlantic Council and have unanimous agreement from it's allies. We know that the USA especially were against this. U.S. foreign policy was somewhat sympathetic to decoloniszation, but only as long as this was not a communist uprising. They feared pushing allies too hard, and France especially was seen as a a lose cannon who might align with the Soviets.

But U.S. sympathies were generally with the Algerians. John f. Kennedy, as a senator, was vocal in his support of Algerian independence, and invited the prime minister to the white house. During the war, there was no appetite in helping a minority of European colonists dominate an Arab majority, especially when they showed no interest in communism. The U.S. was even ready to provide material and weapons assistance post independence in order to keep out Soviet influence.

And without us agreement, article 5 would not have been invoked. The NATO records at the time do not even show France bringing it up, as they knew from bilateral conversions with the USA that it would not be agreed to. The cold war saw a lot of unrest within NATO nations: decolonization in Africa and Asia, military coups in Greece and Turkey, communist terrorism across western Europe, the troubles in northern Ireland. But none invoked article 5, or at least it was never agreed at the NATO level. I think this was because article 5 was really meant to protect europe against a major attack, either from the Soviets, their allies, or an equally large enemy. The allies were , in a way, saving such a declaration for the real thing, a major war.