Nope even today you can still do that, but it depends on alot of things and geo political realities as well.
South sudan fought a bloody 40 years war for independence against the sudanese government and they finally got their independence a few years ago.
In fact I believe if there is a strong case for independence by the vast majority of people in a given region to the point where many are ready to take up arms and die for their freedom or caus,e, then we should let them vote for their independence or not. Be it from chechen Russians, uygurs in China, kurds in iraq/Turkey/Iran and Syria, catalans in Spain, separatist groups/regions in India/Pakistan etc etc.
These countries can all learn from Britain since we had to grant ireland independence as well after they demanded and fought for it, while giving irish people the opportunity to chose/vote if they want to remain part of U.K which northern Ireland voted to remian with us, reason we now leave happy altogether.
We did the same thing with scotland recently(even though we had no real reason to do so, since there was no pressure or call to arms for us to do do).
AFTERALL that's how REAL democracies function. Let the people vote and choose in a referendum. SIMPLE. After that everybody can then live happily ever after, no point in forcing people to be part of a country they dont want to belong.
You should be thanking the U.S,U.K/NATO for taking care of the sunni dictator Saddam Hussein, since if not for us you will still be fighting Iraq for some little scrubs in the middle east. In fact Saddam was crucial in thwarting irans ambitions in the middle East. We removed a big stumbling block for iran by deposing saddam and giving power to your Shia allies/brothers. So if anything you should be happy we intervened in Iraq.