The US is unusual as a federation. Some parts decline, others rise. I think it’s resilient. And every time something goes wrong, America pulls out a magic new technology. We will see if R&D will carry the day again.
The Swiss?
Norway?
And I was in Serbia lately, and while it was not as developed as NW-EU, nobody there described it as decaying (and many said they experiences decay when living in western nations over the past 2 decades).
With OP postulating that it is to enable corruption, and a sub-reply affirming that it is therefore the trait of a country in decay, bringing in Serbia as a counter-example is hilarious.
Serbia ranks 116th in the corruption perception index, Germany 10th. (Lower is better)
There's very little value in a statement like yours. It's a truism that has never been correct.
Maybe the other western countries are equally infertile, but just allowed many immigrants in (which counts are population expansion) that also have more children on average.
How are Japan and Korea holing out? They are further down the infertility down-spiral.
So, maybe rapid growth combined with consumerist impulses is a deadly combination for a society. If only rapid growth were combined with healthy and wise priorities...