How will they contribute to NATO then? Your point was that they don't need political alliance to be in a military one, my point is that this is practically impossible.

Also good luck with making an army from nothing just in time before invasion.

Edit: and you are still ignoring weakness of such states on economic level.

History shows it was possible in cantons of Switzerland, Habsburgs couldn't conquer them, despite no federal authority. There are still examples of small countries in military alliances today - I don't see what is the problem with contributing.

Economics is not a problem in a modern world with a free trade. Small city-states, that embrace free trade, fare well. There is even an possibility, that trade liberalization leads to political disintegration: https://www.nber.org/papers/w6163

Imo Switzerland is poor example and free trade cannot be guaranteed for small states in today's world but I guess we will not convince each other in this limited debate . .. Let's agree to disagree.