Hi, a data point from me flying to Canada this week.

I flew in paid First two nights ago, Atlanta to Toronto. I went to the SC in the international terminal (F), and upon scanning my boarding pass, the agent told me that flights to Canada no longer have access to the lounge due to a recent change in policy. I persisted (not actually having rechecked in the last couple of weeks since initially asking on here) insisting when I booked the ticket I absolutely had access and is why I selected Delta over another carrier, and she relented, and told me I could have access 'just this once' as it was such a recent change, but in future I would not be allowed.