The phrase "each of the countries" is correct and usable in written English.
It can be used to refer to multiple countries. For example, "Each of the countries in Europe have their own unique culture."
Students from universities from across the world take on the role of each of the countries.
Each of the countries on the tour was selected because of its link to Israel.
The rest are dotted line reports in each of the countries, all over Southeast Asia.
The figure below shows the violent death rates for each of the countries above.
Each of the countries in Africa will evolve in diverse ways.
We also found unique groupings of team motivational factors for each of the countries investigated.
Albania In each of the countries where I worked, I wanted to find my unique approach.
For each of the countries, the report lists the actions, from training to financing, needed to augment the existing effort.
In each of the countries, there will be decision makers who are focused on questions that go beyond the region.
We observe similar patterns in each of the countries analysed, suggesting that there are consistent biological mechanisms at work.
Each of the countries had its own university, along with a number of technical and professional schools.
