The important step is to have in place the block for buyers and also check that all your listings are showing no international postage. I have never had to block any countries as long as those two steps are in place.   I did get a couple of buyers from the UK a few years ago and couldn't understand why until I discovered that I still had a postage cost to the UK showing, I had used a sell similar without properly checking everything.

Gosh that was from a long time ago, it hasn't been worth while selling overseas for me for ages.