Ah, there's the catch.
Well, that's not overpowered at all! In fact, now it seems quite situational.
I do find the sheer number of bonuses a bit overwhelming. Jadwiga's UA has three separate components and Poland's UA has two, and then there's also the UU and UB. Seven unique things about a civilization is a lot. I think it might be more elegant to reduce the number of uniques and make them more memorable. Contrast Poland's plethora of bonuses with those of a simple Civ like Greece or Rome; I think the latter kind of design is less cluttered and more effective.
I feel it will only be noticeable under certain circumstances. If they are a near neighbour who you can't fight off, it will be a pain. A distant Civ you won't notice. In multiplayer it will be borderline useless, as you will be unlikely to settle close enough to a rival for it to really matter. If you are Poland in a single player game, then lols all around. So I think it probably sounds worse on paper than it will actually be.The fort ability definitely sounded overpowered at first (and absolutely miserable to play against), but it does seem like they had the foresight to preemptively address the biggest abuses.
I love this tile-stealing capacity, and Poland is cool. I'm just afraid it's overpowered, but you're right, I guess we can't steal wonders, neither districts probably, and that make quite less tiles to steal.
Oddly, no comment on that you will get ONE WHOLE CIV for 4.99. Isn't that amazing?
Situational indeed! Wonders that are in progress gets destroyed if the tile gets taken. So the "culture bomb" ability can be used in certain situations to stop a neighbor from completing a wonder!