how did nationalism started revolutions across europe in 1848?

The French Revolution helped introduce nationalism in Europe, for it changed France's entire system of government, defined citizens' rights, and developed a set of national symbols. The Revolution also spread nationalism to other countries.After Napoleon's defeat, Europe reacted against nationalism for a while. i hope this was helpful <3

regarding the law, the 15th amendment was specifically designed thinking in the rights of black free men.

even though ratified on february 3, 1870, the promise of the 15th amendment would not be fully applied for a long time.poll taxes and literacy tests would allow southern states disenfranchise african americans. only in 1965 the voting rights for african americans would be actually able to vote in the south.

in 1965, president johnson signed the voting rights act, which aimed to overcome legal barriers that prevented african americans from voting as it was guaranteed by the 15th amendment to the u.s. constitution.

some american cities felt workers were being oppressed by business monopolies