hcallega said:
What-if Hoche's invasion force did not fail to land in Ireland? Do they defeat the British? What is the fate of Ireland?
If the French succeed in landing in Ireland, they will have to fight the British troops there alongside the Irish Patriots. They might succeed in putting Ireland as a Sister Republic of France, but I don't think that Ireland would remain independent for long.
The reason? The Royal Navy.
Britain had by far the best navy of the world during the Revolutionnary and Napoleonic Wars. It wouldn't be hard for the British to blockade Ireland, prevent French reinforcements from landing while landing more British troops. The Irish and the French soldiers helping them might hold the British for a while, but they would ultimately loose to the might of the Royal Navy.
On the other hand, an Irish Republic allied to France might be of more concerned to Britain than the events of the Continent. The British might still help the coalition, but they will probably focus on reclaiming Ireland.