First, a few misconceptions about Patrick:
Patrick isn’t really a Saint with a capital S, having never been officially canonized by Rome. And Patrick couldn’t have driven the snakes out of Ireland because there were never any snakes there to begin with. He wasn’t even the first evangelist to Ireland (Palladius had been sent in 431,about five years before Patrick went). Patrick isn’t even Irish. He’s from what’s now Dumbarton, Scotland (just northwest of Glasgow).