why was adoption of the Bill of Rights critical to the success of the fledging American nation?

No because it came after

Originally, the Bill of Rights included legal protection for land-owning white men only, excluding African Americans and women. It took additional Constitutional Amendments and numerous Supreme Court cases to extend the same rights to all U.S. citizens.

no one pays attention to the constitution. vote for Ron Paul.

It was the first document that unified all the colonies and truly made us a nation and marked the succession from the British.

It wasn't critical, it was fundamental a mere recognition of a pre-existing reality. Hardly a new discovery at all only a new recognition.

Because it established the right of lazy students to ask questions on the internet and try to get other people to do their homework for them ...

-Some states required that it be attached to the Constitution before they would ratify it.

-It specifically stated the basic U.S. rights in a clear-cut manner, unlike the British legislation that they felt so oppressed by before.