Bids from countries I don't ship to?

[3islanders]

I offered shipping only to Canada and USA.
I got a bid from a profile in China.
I've dug through past questions on here, (didn't find anything more recent than 2014), followed the instructions to "set buyer requirements"... exclude primary address in countries I don't ship to, apply to current and future listings etc. ... nothing changed on the listing.
So I had to edit the specific listing manually, and blocked other continents.
Now the "buyer requirements" page has de-selected the "primary address in countries I don't ship to" again.
Now what?
How do I get a blanket exclusion or do I have to go through each listing? How come the buyer requirement page went back to its previous setting?

[3islanders]

And wondering if I should cancel the bid or wait and hope someone outbids them.

...ugh, AND, now that I've added exclusions, I see that 2 of the bidders are from excluded countries.

[msau4301]

I have many times seen bids coming in from China, Thailand, Russian Federation & other places I don't ship to currently and several times/most times these bidders have won the address did end up being in the US. (Another case of needless worrying!). Just because it shows the bidders location, doesn't always mean that is where it is to be shipped to....especially in cases (like mine and possibly yours!?) where I do not ship to all international destinations. If you show shipping to Canada and US only (as I have done for these past couple of weirder-than-normal years) I don't think bidders can get through unless they have an alternate address (forwarding location) in Canada or the US.