Wouldn’t it be best to have historical and ahistorical options, in which we can either ply with the countries as the world as we know them, or have either a bunch of separatist movements work historically, or for a lot of countries to unite.
And these modes can have pros and cons.
Pros: USA has a lot more power (assuming the states don’t secede), and can play them off each other so to those countries having conflicts between each other. State Department doesn’t have as many big crises.
Cons: USA has to juggle a lot of conflicting interests and alliances between those many countries. US State Department has to have an even bigger headache dealing with all this.
Pros: Countries are more effective and united, and goals are simple and non-contradictory, and winning then over means a greater net gain of power. State Department has much fewer messes to clean up,
Cons: US bargaining power reduced due to these being more powerful countries. USA can more easily find itself isolated by countries uniting with common goals. Any international issue is multiplied exponentially by the countries having much larger importance.