primary country division tier
The first level of subdivision inside a country, whatever that country calls it.
The primary country division tier holds the first level a country divides itself into: the state, the province, the region, the prefecture, the governorate, the voivodship. What the unit is called is the region type; the tier says only that it is the first step down from the country.
Placing every country's first level on one tier is what makes them comparable. A German Bundesland, a French region and a Japanese prefecture differ in powers and in size, and all three answer the same question about position.
Where a country has no such level and its municipalities sit directly under it, this tier stays empty for that country rather than being filled with something invented.