Easy setup of Shipping zones internationally

Right now if I want to ship internationally i have to make a zone and manually select all countries.

I want to do a product that's the size of the letter, which means I have three rates:
-Canadian stamp pricing
-US stamp pricing
-International stamp pricing

So it's very easy to set up the Canadian and US zones, but when I went to set up the international zones, I can't see an 'all countries' option. It would be great if this was an option and it just excludes any countries that have already had zones created. I get the occasional reader from varied countries I wasn't expecting, so while I could go and cover some of the major bases, there will be ones left out.