The Church and the Crusades.
Explanation:
It were the Church and the Crusades that helped in uniting the kings and the people of Europe. When the kings were facing the hardships during the time of people being rebellious to fight for their rights due to the parliament’s harsh policies, the churches and the crusades issued various norms and policies that helped the King in making peace with their public. The Church brought various actions that helped in restoring people’s faith and trust back in their kings. Though the rebellions still fought for their rights, but the mass level saw a decline in number because of church’s policies.