What impact did the Kansas-Nebraska Act have on the old Missouri Compromise line that had been the longtime border for slavery?
It allowed the expansion of slavery north of the 36°30' line.
It had no effect Kansas was below the line.
The line would no longer be valid.
None, it just moved the line further west.

1. It allowed the expansion of slavery north of the 36°30' line.

2. The line would no longer be valid.

Explanation:

the kansas-nebraska act of 1854 (by Senator Stephen A. Douglas) repealed the missouri compromise of 1820. the missouri compromise had prohibited slavery north of the line 36°30' but because of the kansasa-nebraska act, that line wasn't valid anymore, and without that line being valid, slavery expanded north of the 36°30'. this act was supported by pro-slavery people but was not supported by anti-slavery people.