It is then also an alliance of Imperial core countries (it was after all, founded in response to the Warsaw Pact).

It was NOT founded in response to the Warsaw pact. NATO was formed in 1949. The Warsaw Pact was founded in 1955. The Warsaw pact was founded in response to NATO. NATO was building up West Germany economically less than 10 years after the fucking holocaust. The Soviet Union tried to join NATO in 1954 and was told "no, you aren't democratic enough." But they had no problem letting West Germany in while integrating "former" nazis like Adolf Heusinger into their command structure.

I mean, it is literally a defensive alliance if only because if one country is attacked, the others are legally obliged to treat it as an attack on them

less than a third of NATO countries were admitted to NATO through some kind of democratic referendum. It was almost always the unilateral decision of the given country's bourgeois class, rather than something the people themselves were consulted on. In the cases where democratic referendums were held, it was often in countries that had just been balkanized (former Yugoslav countries, for example), or countries that were just at the outskirts of NATO and were therefore pressured geopolitically into choosing whose "sphere of influence" they were under: Russian federation, or USA. When a nation is compelled under duress to pick sides like that, and a class dictatorship of the bourgeoisie is the one that usually ends up making the decisions, I doubt the alliance can reasonably be called "defensive." Its borders keep expanding to encircle and balkanize nations whose main "crime" was being socialist Once Upon A Time. NATO expansion is marching us towards WW3. It is an expansionist and aggressive alliance that merely uses Article 5 to appear defensive and Democratic, while trying its hardest to constantly provoke wars and lay claim to natural resources.

Is the following something a "defensive" alliance does?