What would the reaction of westeros be if knowledge of jon’s true parentage and the events of the tower of Joy were somehow publically revealed after ned and roberts death?

After both their deaths? I think it’s much trickier than people think, and it’s not going to be a case where everyone rushes to declare for The Hidden Prince. There’s going to be a lot of Baratheon loyalists, both of the Lannisterian and anti-Lannisterian varities, the North has declared its independence (the Iron Islands too, come to think of it), and there are rival Targaryen claimants who would dispute Jon’s right even if it were known that he was definitely legitimate.