Make sure to reverse all applicable portions of the argument, or it won't make sense (and even then it's not necessary that the reverse be true for the argument to be true).

It's more akin to a friend who has a terrible job spending a few days working at a good job and realizing their job is terrible (to keep it reversed), or like a friend that has a good job but thinks it's terrible spending a few days actually working a terrible job and realizing how good theirs is (to keep the argument the same as AJ007 presented).

No, because the original view was still of something bad (corrupt first world governments). They aren't as bad as something else (corrupt second/third world governments), but they aren't good.

So using jobs, it is like having a job where you have to often pull 60 hours weeks and then having to spend a few days helping a friend pulling 80 hour weeks (with same compensation). Even then, the 60 hour weeks being the norm is a bad thing and saying that someone shouldn't feel bad about it doesn't make sense.

The switch was from bad/worse to good/better.

It's all about relative experience. Your 60 hour a week job may not be good, but you may be able to see and appreciate the parts that aren't as bad as what you've now seen, and even a great job may not look as good after you've experienced the perfect job.

And to be clear, I don't think the cure for thinking that "(insert first world country) is absolutely terrible" is now good, just that it's relatively better than the initial assessment.

To get back to your original response, it's like telling your happy friend they shouldn't be absolutely content because yes, there are people out there that are doing better financially (assuming you are willing to equate financial success to happiness). It won't make them happier, but it will make their outlook more realistic (which isn't always a good thing). But again, reversing the statement like that doesn't preserve it's logical attributes. e.g. If A implies B, you can't infer that B implies A..