There’s an imbalance, yes. Some places have fewer dogs to pick from, or a smaller breed selection, and all this is cultural.
Places that are mainly white, educated, middle-class, are where most people spay/neuter or don’t breed their dogs. There has also been a huge shift in the way the general public views registered purebred dogs, which since the Victorian era have had a lot of cachet (the purebred dog industry had a lot to do with its own decline). Now, the cool thing to do is "rescue’. If that is your aim, you are going to be dependent on the stream of puppies produced by the non-middle-class and non-educated and non-white. Mostly those are going to be pit bull types, random mutts, and rather misshapen toy breeds.
In poor areas dogs and puppies are dumped out of cars on deserted roads all the time. ALL the time.
In the middle class, there is such a desire to feel virtuous about “saving a life” that street dogs are now imported from Mexico among other places, for adoption in the US. This is causing concern because these dogs are bringing in interesting parasites and diseases not normally seen here.
Nothing simple about the dog thing.