Stephen douglas! <span>ʕ•ᴥ•ʔ</span>
Russia refused to abolish serfdom and its agricultural past.
Agriculture was technologically underdeveloped and remained in the hands of serfs and state peasants. they were large estate which accounted for about 20% of all farmland but few of them were worked as large scale unit.
During that era, the states in America was divided between Free states (where slavery is not allowed ) and slave states (Where Slavery allowed)
Back then , Texas and Florida got a lot of plantations that's heavily depended on slave , so if they were acquired , they would be part of slave states.
This will destroy the balances between slaves and and free states in the congress , ( the slave states congress will have the majority power), so the statehood was delayed