West Virginia is probably too big of a lift, and Oklahoma is no better than a tossup in my opinion.
Ironically, if he wins, even if it was to be only extremely narrowly Trump might have a better chance at winning a county in every state.
The only state where Trump failed to win a county was Massachussets, where the closest county was Plymouth County at Clinton+7. That county was won by the R senate candidate while losing the state by 3 points less than Trump (60-36 instead of 60-33).
So if Trump rebounded compared to 2016, even by just a bit in Massachussets he might have a shot at winning the county, but it is very much unlikely.
Of course with Trump being down by around 8 as of now, this is an extremely unlikely scenario. But if say, Trump won the Popular Vote, he might win a county in every state.
As for places where Biden might add clean sweeps, other than Rhode Island there aren't that many of them. VT and CT are the next 2 in line, but Litchfield and Essex are probably too Republican for Biden to win. Delaware might be doable if Biden gets a big "favourite son" effect but it is also an unlikely one.
This is incorrect. Clinton also won every county in Hawaii. No Republican has won a county in that state since Ronald Reagan in 1984 (which was also the last time that Hawaii voted Republican in a presidential election), and the closest county was Honolulu County, which Clinton won 61-32% over Trump. Honolulu County is the state's most populous county, and has been its most Republican one throughout it's history. So Trump's chances of winning at least one county in every state are virtually nonexistent.
Oh yeah forgot about Hawaii. Yeah Hawaii makes it impossible for Trump, even if he did win big.
He just has to appeal to the former leper voters of Kalawao County. Surely he can at least manage to expand his appeal enough to do that, right?