Similar to how hero has an easy to access exp bar, I believe kingdoms too should have an option that allows their exp progress to be displayed in a more intuitive way. It could be a toggleable option that by default would be off as to not confuse newer players, which would simply show a exp bar under each kingdom. It would help a lot in deciding which kingdoms need further progress with troops and traits. In the current system, it takes minutes on end to check every single kingdom’s exp to see how close it is to the following level. If a toggled option was added for the kingdom map, it would take seconds to figure out which kingdom(s) are close to progression and may even encourage players to get those few extra keys to reach that next objective.
Something along the lines of this: