I’m thinking - the treaty was signed in April 1949 and was definitely underway by April 1982 when the Falklands War began between Britain and Argentina. On 2 April 1982, Argentine forces moved onto the islands - If this was considered an act of war, then did Britain try and enlist the help of its NATO allies? I don’t recall reading anywhere that this was done. If not, was it due to anti-imperialism?
No, because Article 6 of the North Atlantic Treaty limits the scope of Article 5 to Europe, the Mediterranean and the north Atlantic, defined as north of the Tropic of Cancer:
For the purpose of Article 5, an armed attack on one or more of the Parties is deemed to include an armed attack:
on the territory of any of the Parties in Europe or North America, on the Algerian Departments of France 2, on the territory of Turkey or on the Islands under the jurisdiction of any of the Parties in the North Atlantic area north of the Tropic of Cancer;
on the forces, vessels, or aircraft of any of the Parties, when in or over these territories or any other area in Europe in which occupation forces of any of the Parties were stationed on the date when the Treaty entered into force or the Mediterranean Sea or the North Atlantic area north of the Tropic of Cancer.
An exception was made for the now-defunct French Algeria which had a small part south of the Tropic, but not for the Falkland Islands, Saint Helena etc.