Does weather cancellations at an airport effect all airlines flying in?
Theoretically, yes. I have found no reliable way to prove this other than comparing my departure punctuality to another airline(s) hubbed at the same airport, and I have seen that in those cases both/all of us saw significant drops in our on-time ratings. But whether it affects foreign airlines flying in, is hard to quantify since one canceled flight hardly shows up in their public statistics.