There is probably another issue you facing because your page should load
normally the full list.
If you use the "Generate Tag" you choose Drop-down menu and give in (the field named Choices, 1 on each line!) all the countries you wish.
Look here (image), works like a charm.
Still having issues? Check your other code because this (as shown on img sample) is as it has to be.
Still not convinced, look also here.