My mom recently passed away and she lived in PA. Since I live in CA, what happens in the tax world with the proceeds from the sale of the house?

Your mother's estate may or may not owe estate taxes to either the IRS or the state of PA - however if the value of the estate is less than $2M the estate won't owe any taxes. Hence the full value after expenses will pass to the heirs. As an heir you will not owe anything to CA, as there is no inheritance tax in that state.

Agree!