I think the better example would be everyone grabbing a sandbag. It's not going to stop the flood, but it can protect some buildings. Your example is bad becaus

I think the better example would be everyone grabbing a sandbag. It's not going to stop the flood, but it can protect some buildings. Your example is bad because you posit everyone making individual changes will make no difference. That is false. Everyone acting together will not solve it, but it will make a dent. Your order of magnitudes are off.