In "The Queen's Justice", the third episode of the seventh season of Game of Thrones (S07E03), Jon Snow, King in the North meets with Daenerys Targaryen, "Rightful Heir to the Iron Throne etc."
Towards the end of this scene, Daenerys says that she is the "rightful Queen of the Seven Kingdoms" and that by Jon Snow declaring himself "King in the North" he is in open rebellion.
However... Jon Snow, and the North, isn't in open rebellion against Daenerys, but against the Iron Throne as it currently stands, which is held by Queen Cersei Lannister (of House Baratheon). I would expect that Jon Snow knows this (though his reaction to her words may say otherwise). In fact, Daenerys is currently a foreign invader, whose only earned titles are Essosi (her Westerosi titles are hereditary and debatable, not for discussion here). Jon Snow holds no fealty to Daenerys and therefor has no obligation to support her cause.
It is true that Torrhen Stark bent the knee to Aegon Targaryen, however this oath was broken around 24 (I think) years ago when House Stark joined House Baratheon in a rebellion against Targaryen rule -- I don't imagine that this oath could be considered intact when it was never reformed after the rebellion.
Based on this, my question (based on much internal deliberation) is: Should a Westerosi house that broke an oath of fealty with another Westerosi house be expected to continue to support said house when demanded by a descendant of the latter, particularly when said descendant holds no Westerosi titles?
I understand that is a tightly defined question, please let me know if I should break it up a little more. Given that the question calls for information from history and established lore, information from the Books, TV Shows and GRRM himself should all be applicable.