Australia has a similar problem to the USA. It costs a lot of money and it's very difficult to import other animals; trying to get in as a human isn't easy!
There are black market imports; there is a thread here on BYC about BCM's which I suspect are such imports.
As you write, we do the best with what we've got. It doesn't later the facts though. The breeding stock isn't adequate in any form to cater for demand. A handful of a particular breed are probably being bred generation after generation without new blood. The outcome is inevitable if they are being bred to a standard and one assumes, to make a profit.
Fortunately here in Europe and in Asia, China and many other countries importing is a lot easier. It was possible before Covid to drive to say Egypt, check around the farms and bring back some chickens. I can go to France, or Germany for examples and bring up to five chickens without doing any paperwork, or paying any "duties".