Honestly, even with all its problems, the USA is still doing OK compared to other major powers.
* China has a looming
demographic crisis. It's wealthy coastal regions surround a poorer interior that's slightly richer than sub-Saharan Africa. China's strategic position is also bad: It's boxed in a remote corner and surrounded by hostile countries that prefer to align with the USA. Its exports and imports (especially oil) cross the straits of Malacca, which is easy to blockade. It has a lot to fear from the American and Indian navies, as well as a potentially resurgent and rearming Japan.
* Japan also has a demographic crisis, caused in part by a decades-long recession, in part by a hyper-compartmentalized lifestyle that has led to social atomization.
* Brazil is still a poor country and a political mess.
* Russia's GDP actually fell last year.
* In the UK, Brexit seems to have under-delivered. (I presume that a full recovery will take some time).
* France has tensions vis a vis existing North African immigrant populations. Reactionary thought and
far-right figures have been on the rise for some time now.
I could go on, but the point is that all countries have social problems that are often deemed existential in the moment, but which aren't uniquely bad when looked at from a bigger perspective.