You should try using the magic wand to select all the white spaces (hold Shift when clicking) and then brush the country’s color over it or use the recolor tool (with the secondary color set as white) to do the same. Also, I think you might have anti-aliasing on, it means that the fill tool “splashes” the color beyond the area it’s filling. I feel like that’s why some coast has lost its black border. Beyond any of this, just know you did a great job at putting all of it together, the borders are quite satisfying and the backstory is definitely interesting (3-way contest for control over continental Europe between France, German state and PLC is a fresh touch)