How did the Constitution create a stronger unity between the citizens and the states?

The Constitution helped to create a sense of unity between the citizens and the state governments. Because the Constitution gave certain powers to the states, the people believed they were able to help shape state policies. The people were able to elect representatives to the state government. These representatives made the laws in each state. Since the people elected them, the representatives needed to listen to the wishes of the citizens. Also, by granting the states certain powers, they were able to control, to some degree, what the federal government was doing.
Additionally, the people were able to elect representatives to the House of Representatives. These elected officials also had to listen to the people they represented. This furthered the idea that the power remained in the hands of the people and reflected the idea that government is based on the consent of the governed.
People in each state felt a closer connection to the government than they had when the British ruled them. The colonists believed the British Parliament and King didn’t listen to or represent them. This changed with the adoption of the Constitution and created a stronger sense of unity than had existed in the past. The people believed that the government represented our collective voice, which was an improvement from the days of British rule.
https://constitutioncenter.org/learn/educational-resources/historical-documents/perspectives-on-the-constitution-understanding-our-constitution