This is not a complete answer, but there is evidence that crow populations are rebounding. From The Virginian-Pilot, July, 2017.
Crows? Who’s been seeing and hearing a lot of these noisy raucous
critters this year?
I certainly have. The big black birds are raising Cain, up and down
the North End.
This paper is based in Norfolk, about a four hour drive from my house.
It is a far from a scientific article, so I won't quote more.
According to the St. Louis Post Dispatch, February 2013, crows are returning to the Midwest.
The Audubon Society’s Christmas Bird Count indicated that the bird [crow]
population may be back to pre-virus levels in Illinois, and recovering
part of its numbers in Missouri.
They’re almost back to where they were 10 years ago, said Robert Russell, a biologist at the U.S. Fish and Wildlife Service, referring
to the Midwest. Our crows are pretty much back to normal.
Crows were especially hard hit by the West Nile Virus:
The death rate for infected crows was 99 percent when the disease
first appeared in 1999.
There was, as of the publication of this article, no definitive explanation for the resurgence of the crow population:
No one knows why the crows seem to be returning now. West Nile is
still with us, although at reduced rates. There were 21 human cases in
Missouri last year, compared with 168 a decade earlier.
After the worst years for bird kills, scientists sampled birds to see
if they were developing antibodies to the virus. “We didn’t find any,”
said McGowan, the Cornell crow expert.
The answer might lie in a sort of high-speed evolution. The crows that
survived have the most natural resistance to the disease, and they’re
passing it on to their progeny, said Geoff LeBaron, the ornithologist
in charge of the Audubon bird count.
In 2014, Bay Nature reported increasing crow populations in Berkeley, CA, possibly attributable to the birds' intelligence and adaptability. (There was not a dieback of crows in Berkeley.) According to the Cornell Lab of Ornithology, WNV became less lethal as it moved west and was less lethal to crows in diverse habitats. Going beyond crows to some other species of birds, the picture is not so happy, but this is beyond the scope of the question.