Given that other nations still had slavery why did the abolitionists believe that the guilt for such oppression lay more heavily on the united *** states? and why did they accuse the national and free-state governments of aiding and abetting the southern states in the continuation of slavery?

The US was the 'city upon a hill': Using early Puritan ideology abolitionists saw the US as a beacon of equality and freedom which slavery spit in the face of. 

The US had been a model for political philosophy and an experiment which was mostly a success but slavery was a flaw. Abolitionists believed we could not be a beacon of freedom with the system in place. The US government refused to deal with the issue and compromises furthered the practice instead of limiting or eliminating it. 

North korea has been ruled by dictator since 1948