Here's an idea that might help make the player feel like their actions are giving their nation a distinct culture:
A "capital city screen", in which you can view a visual representation of your capital city, based on 1) it's geographical location 2) it's population 3) buildings and people determined by your actions eg. if you're an aggressive, warmongering nation then you'll see large forts and barracks populating your city, whereas if you're a particularly diplomatic nation with lots of international ties and treaties then you'll instead see embassies, grand palaces to wow visitors etc.
And let's say every capital city has a market - the size and grandeur of the market is determined by your wealth, and you can click on the market and see a big stalls showing some of the kinds of foods available to your citizens, this being determined by who you have visualised, where you have colonised etc. so for example if you are playing Tyrone and you have some caribbean colonies, you'll see irish food like fish and european veg and soda bread, farls etc, but also mangos, tropical fish, coconuts etc.
And then you could click on an art gallery and it would show you paintings, perhaps real historical ones perhaps not, from painters that have emigrated to your nation from other countries that admire yours, and the quality and number of paintings is determined by your nations cultural strength.
You could also perhaps gain bonuses by upgrading certain parts of your capital, eg. for 1000 ducats you can upgrade your palace and gain a bonus to diplomatic skill and prestige.
Mousing over different residential parts of your city you might be able to see what the main ethnic groups of your nation is eg. the jewish quarter, the irish quarter, the french quarter, the wallachian quarter. The religion they bring and the religious situation of your own nation will cause different places of worship to pop up. And depending on your sliders the distribution of wealth in your nation may be seen as either grand villas for the rich and slums for the poor, or relatively equal housing for all.
I don't know if you guys are really as interested as me in EU having this kind of thing, but I really want to be able to look at my kingdom after a 100 years and see how my actions have affected it culturally.
The idea of a capital city screen was ofc first used in AoE III: