The Kansas-Nebraska Act of 1854 and the repeal of the Missouri
Compromise led to what unexpected outcome?

contributing to the collapse of the Whigs and spurring the creation of a new, broad-based anti-slavery party known as the Republican Party. Most Free Soilers joined the Republican Party, which emerged as the dominant political party in the United States in the subsequent Third Party System (1856–1894)

Explanation:

https://en.wikipedia.org/wiki/Free_Soil_Party

a. competition between france and england for land and power

they made rome the dominant power in the mediterranean.