https://www.posti.fi/fi/asiakastuki/lahettaminen/maakohtaiset-tiedotThat is the similar page of Finnish post.
situation varies almost daily. Now you got latest update of countries done 27.3.2020. It seemed pretty good. USA and Canada still works. Rest of overseas not at this moment. Europe pretty good in general, almost every country is ok.
Problem is mostly the lack of planes. As far as I know, big part of letters and smaller packs travel in cargo of regular passagner flights. Now that there is not much of those planes flying, it means there has to be new routes, new deals made with alternative ways to get shipments where they have to go.
All mail from Finland to USA, goes to JFK airport, where it proceeds further. So if New York problems increase, it means problems to mail sent anywhere in the US.
Some may say that the past lifestyles is gone, and things will never be the same... but I would not consider non-existing postal system as option. It just adjusts itself into new ways. Drastic pace of change causes some turbulence. I would not worry much about placing orders from and to countries that are not in border of collapsing. Most of post is slower, as the alternative routing even in EU means basically trucks. If there are no planes for priority mail, they'll just use trucks instead.