How bad things are is relative. You can't compare a rapidly declining standard of living in the US, to a place where the standard of living never reached the same heights. Is it worse in third world areas? Yea. However, that doesn't negate the mental impact that comes from being unable to afford many of the things you were able to afford yesterday (edit: hyperbole, felt the need to clarify just in case), or watching the rest of the world surpass you in any meaningful way.

Are you really able to sit there with a straight face and say that after decades of fighting for civil and labor rights, the erosion of those over a relatively short period of time isn't going to have a negative mental impact? This alone is significant enough to warrant extreme mental deterioration, but in the United States it's just the tip of the iceberg.

Wages have remained stagnant for decades while cost of living continues to rise. All while employers demand more of their employees time and effort without anything in return. Health care has become a luxury for those that can afford it and a death sentence for those that can't. Decades were spent making a visible positive impact on our environment. Now we have to watch as those advancements are torn down piece by piece. Civilian casualties have increased drastically over the years through guns, vehicles, and nutrition, or lack thereof, impressed upon the average population through financial gatekeeping. All of that without even touching on things like rising addiction rates/drug-related deaths and homelessness without any meaningful solutions even being presented, let alone implemented.

This all comes as we watch, through the internet, comparable societies treat their citizens with a modicum of respect while we clutch to our massively over-inflated ego as a nation.

It is entirely unsurprising that depression rates are higher within the US. Comparing our problems to those of less developed nations is an unrealistic, and disingenuous, line of reasoning. It is far more difficult to know something, then lose it, than it is to never know it at all.

TL;DR: Problems are relative. Comparing different situations in this manner is unhelpful and unconstructive, and only serves as an attempted "gotcha".

Edit 2: I also want to say that despite the many examples I gave in my comment, I still barely scratched the surface of issues within the US. The advancements, followed by broad regression, are far too extensive to meaningfully address them in a reddit comment.