Do you seriously expect to see a notice on eBay.com every time a postal service somewhere has a labour disruption? If you do, France, Italy, Spain would be on there almost weekly.
As far as Canadians shopping on .com, don't you think Canadians are aware of the potential int eruption and don't you think that US sellers who have a lot of Canadian buyers would be making alternative arrangements.
If buyers are so clueless about these situations what makes you think a warning on the home page would do anything?
Although it didn't happen until today, eBay did send a notice to US sellers about the possible strike:
http://announcements.ebay.com/2016/06/potential-canadian-postal-strike/
The announcement also mentions that delivery time estimates will be extended and MBG claim timelines extended.

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915
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