My Prussia game was much the same way. As Brandenburg, the only way I could fight anyone else was with vassals, and then I became the HRE. Then two imperial reforms made me hereditary ruler and ALL imperial states my vassals. I must admit though, it made forming and conquering Germany more difficult.
Also, look at all those colorful blotches in the Americas. Is that the Inca in southern Brazil?
As Brandenburg, I had to use sneaky, underhanded tactics to prevail at first.
Poland fighting the Teutonic Order? Attack the order!
Poland in a war against someone other than the Teutonic Order? Attack Poland!
Pomerrania distracted by a war? Sneak attack, then vassalize.
And so on.
As a larger Brandeburg & Prussia--especially after the military reforms--I could afford to be a bit more straightforward. Though, being surrounded by a blobbing Bohemia, a Blobbing Poland, and a Blobbing Sweden (!?) made things a bit touch-and-go at times.
Looks like Milan to me.
Yeah, it's Milan. They've got colonies everywhere, ensuring that I'll never wipe them out or vassalize them, because I've been focusing all of my effort on land warfare and just let the dozen or so vassals of mine that have navies handle the seas.