As far as I know, no, its not just about the US. As I believe I said, from what I've been able to determine there's quite a bit of uncertainty for sellers in the EU about mail transit networks to North America period. Maybe these countries are unusual for you, but they aren't to me....I have a lot of European customers who send a lot of money my way, and its important for me to know what markets are or aren't safe to re-enter with all the chaos, lack of information and potential misinformation going on.
Anecdotally I have heard that stuff is getting from Canada to the UK no problem, glad to hear its getting back. I did just speak with a long time customer in Germany who has ordered stuff from Canada and Japan within the last month and he told me two items from Canada have gotten there in 10 days (normal pre COVID time frame) and 12 days on the other from Japan. No tracking all regular parcel mail for these three items.
Interesting you mention Greece as I spoke with a seller there and his exact words to describe his seller experience currently were "its total chaos actually"...he said the system is very backlogged, and there is no information on international service delays from the Greek postal service, and what info they do get changes daily.
I expect the experience will be different depending on what country the person is in, but I suspect the experience in places like Belgium, France and Switzerland may be similar to Germanys, but without information from those countries I cant conclude that for sure.
Personally I've ordered two items from the US in the last month, one on April 17 and the other on April 19. I got the April 17 item on May 12th and am still waiting on the April 19 item. Both from the same company. This scares me a bit as a seller, given how twitchy Americans tend to be about late deliveries.
