Atheism is not a "unifying" force nor is it intended to be. Atheism is not a religion nor a political system and there is no central organizing entity. Since atheism is not driven by any strict set of doctrines and atheists have no motive to take control over other people, force people to become atheists or rule the world, atheism is a relatively benign personal choice to not accept a belief in the supernatural.
Atheism is working on it.
The event after 1789 that helped to unify the nation is The American Revolution.
no
Italy was the European nation that did not unify until later. It was divided into many states.
Duke smiffs
Parliament
In 886.
The American Revolution.
Parliament
The American Revolution.
using the market system
A nation state gave early people's far more security and a better understanding of their common language and history. These things unify a nation state and give the people within a reason to identify with said state.
it didn't help with anything