Liberty Enlightening The World
It shows up in the tab after 1850 if France is either a HM's Government or a democracy and if the USA exists and owns New York. All of these requirements are present at the start of the game except the date of course. It is possible to take once France have researched Cheap Steel.
The AI will take the decision if the relations between France and USA is better than 50.
The event will give USA a modifier, which gives a staggering +500% assimilation rate and 200% immigration attraction. On top of that it gives +0.04 prestige pr. month. The effects lasts until the end of the game. USA already get the highest number of immigrants and assimilation due to being a democracy in the Americas and because of the American decision The Homestead Act, which gives 50% immigrant attraction and assimilation.
The Strategical considerations
From a French strategical viewpoint, it is not a good decision to take as it helps a great power competitor a lot with minimal actual advantage for France.
If the player controls USA on the other hand, it is advantagious to improve relations with France in order to provoke the AI to take this decision.
It has been almost 100 years since France, and General Layafette came to the aid of the brave young American republic in her birth and most dire need. Since then, the American republic has served as an inspiration to freedom loving people everywhere, and has stood as a clear and voiceful reminder to the world of the possibilities of human liberty. Some within the French republican circles have suggested we celebrate this centennery by presenting to the American people a suitable gift to mark their first 100 years as a free people, and their historical bond of friendship with the French nation. Vive la liberty!