I believe the 1-2 per year is the number of attacks on humans in California. Most of the websites are old, so they only give data for the period 1985-1995. I didn't find data for all of North America vs just CA, either. But I didn't look very hard.

One thing is certain, the population of mountain lions is growing and especially in areas that put them in contact with humans. So pure statistics would lead to the expectation that attacks will increase.

I recall hearing once that more people in the US are killed on average than any other natural phenomena. And half of them are on the golf course...