The parasites that frogs have can be dealt with by the snake's immune system (the ones in pinkies may or may not meet this criteria).
I am interested in knowing what sorts of parasites pinkies contain that can be transferred to snakes. Especially the lab mice that people tend to use to feed their reptiles. As far as immune systems dealing with parasites, isn't is possible that an Indonesian snake being fed fish from other countries may be getting parasites from those fish that it's completely unaccustomed to dealing with? Wouldn't the same be true when feeding an Indonesian snake American frogs?

Fish and frog parasites are not the same for all fish and frogs worldwide. For example the tapeworm Diphyllobothrium only appears in freshwater fish found mainly in temperate and subarctic regions. Are you saying Indonesian Garter Snakes are equipped to deal with this parasite?

That said, if you are up to it, it is better to grab a few adults and breed them in captivity than collect them from the wild en masse.
There are very few, if any, people who have successfully breed North American treefrogs. It is very difficult (and far more work than keeping snakes).

Snakes in the wild die from their parasite loads all the time.
Do you have any references that document this? I've never heard of a wild snake that died from parasite overload. The "all the time" line is intriguing. That would imply that there's plenty of proof to show that this happens. Are there any books/papers that indicate this?