Short of attacking a NATO country, is there any other thing Russia can do to trigger direct American military confrontation?
The key section of the treaty is Article 5. Its commitment clause defines the casus foederis. It commits each member state to consider an armed attack against one member state, in Europe or North America, to be an armed attack against them all. Upon such attack, each member state is to assist by taking "such action as [the member state] deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area."
Article 5 states that an attack to one of its members should be considered an attack against them all. This means that an invasion or an attack against a NATO country would trigger military intervention against Russia. But short of Russia attacking a NATO country is there anything Russia could do that might trigger direct American military intervention that's mentioned in a treaty or some other international document?