How did the Kansas Nebraska act lead to civil war?

Answer 1

It allowed the citizens of each new state to vote whether it should be slave or free.

The trouble was the system of letting each state vote, one at a time. This attracted every bully-boy from both sides to invade a small and thinly-populated area, and intimidate the voters.

When it was tried for the first time, in Kansas, the result was called 'Bleeding Kansas', and historians regard it the curtain-raiser for the Civil War.

Answer 2

The weakness of the Kansas-Nebraska Act was that only one state would be voting at a time.

This was a magnet for every bully-boy in America, from both sides, to cross into this one thinly-populated area to commit mayhem.

It demonstrated that the slavery issue would never be settled, except through bloodshed.