A. solve the slavery issue.
The Constitution did not provide a clear solution to slavery. Nearly all of the founding fathers were against slavery, yet still owned slaves. They realized the economic and societal influence of slavery was too great. Founders such as John Adams, Alexander Hamilton, and Benjamin Franklin sought for the abolition of Slavery, but were overridden by the opposition.
The word Slavery was never mentioned in the Constitution to avoid controversy.
I believe it is the last option
Americans developed a concept known as "manifest destiny" in the 1800s. This was the belief that it was their destiny to conquer the Americas, and that this was both tenable and unavoidable.
People not wanting it. and increased taxes