Citizens Rights: the constitution as a legal document enforced in all 13 colonies (at its inception) was crucial in securing a persons right to life, liberty, and the pursuit of happiness through the ability to have legal protection of these.
The Economy: having a unified government is crucial to maintaining currency and in this case it would secure the financial future of the nation and its ability to expand.
National Security: Again, having s unified government would allow for a regular army, rather than multitudes of irregular state militias. This, along with the right to bear arms (2nd Amendment) would ensure the constitutions legality was upheld against those who would tear it down, be it from inside or out.
Hope these points help you!
