I couldn't generalize France's roads, but Ireland is a scary place to drive. I'll most likely never rent a car.

It's like the roads are made windier and scarier on purpose.
Come on Ireland is a fun place to drive, you just have to take into account that there is a fair chance that the driver of the next car doesn't have a licence and shouldn't be let anywhere near a motor vehicle ...oh and in certain parts of the country add in the factor that they may be very drunk as well .
As for the windy roads , that is normal , you couldn't expact an ass and cart to go up and down all the little hills so you build roads that go around every little bump in the landscape . Imagine the lunacy of changing the nature of roads just because of a passing modern fashion like automobiles