Minor Kingdoms

Not so much a specific nation, rather this is a broad category of nations. Minor Kingdoms usually consist of a single large city and maybe some outlying territories. They tend to come and go over time.

A monarch of a Minor Kingdom, if they are even using a that style of governance, will have no more than two vassals. Many have no vassals at all.

Any country of a small size is usually referred to as a Minor Kingdom, regardless of political system used.