Well if you're smart like me because I know history and you don't because your parents washed your brain with propaganda.
Eritrea is a country.
Eritrea was carved out by the Italians and they won independence again from Ethiopia.
Somaliland is a country
Somaliland was carved out by the Brits and they won independence again from The Democratic Somali Republic.
These countries were the same to their neighbours but had different political views.
South Sudan was never a country
They were carved out by rebels and the Sudanese government
They were not even a colony during colonial rule.
They have ethnic violence now.