Nationalist movements will resort to violence if some see it as advancing their cause.
When it comes to colonial powers what comes to mind? I would imagine that you would first proffer countries like England, France, Belgium, the Netherlands and Germany. Even Italy had an overseas territory in the Horn of Africa and Libya. All these lands eventually gained their independence, some after genocides (e.g. the German colony in SouthWest Africa).
Did you know that the US was also a coloniser?
We of course usually see the US as a FORMER colony, that of England. The tale of the American Revolution is a well-known one, a national myth that the US still rolls out to demonstrate patriotism.
But the US has also taken over lands which became, for all intents and purposes, overseas colonies. Examples include the Philippines (1895), Alaska (1867) and Hawaii (1898). The latter two were incorporated as states into the Union in 1959; the Philippines became independent in 1946.
And then there is Puerto Rico
The US acquired Puerto Rico from Spain following the Spanish-American War and the Treaty of Paris in 1898. Although residents were made citizens of the US in 1917 and can now move freely to the US, the island is still an “unincorporated territorial possession” under US law. It is not a state and there is little sign it will become one soon.
There is a fringe movement that really does not like to be part of the US. In a 2012 poll only 5% wanted independence: over 60% wanted US statehood. On occasion those who want to be free have resorted to violence.
Fraunces Tavern bombing
On January 24, 1975 a “thundering explosion” ripped through a 19th‐century annex to historic Fraunces Tavern in lower Manhattan, killing four people and injuring at least 44 others. Police believed that the perpetrators were Puerto Rican nationalists: an hour after the blast callers identifying themselves as members of Fuerzas Armadas de Liberacion Nacional Puertorriqueña (F.A.L.N.), claimed responsibility.
Their statement cited a ‘CIA ordered bomb’ that killed two young workers who supported Puerto Rican Independence in a Mayaguez, Puerto Rico dining place on January 11 that year.
It is hard to imagine analogous violent movements today which would resort to this tactic. Puerto Rico is a fairly stable place, but anything could happen.