Trump's lead among white voters has all but vanished.
Anything like it threatens longstanding GOP structural advantages https://www.nytimes.com/2020/07/24/upshot/biden-polls-demographics.html

It's not easy to imagine the consequences of this kind of demographic shift, but they are potentially very significant.
For illustrative purposes, consider a simple simulation: apply the shifts in national polls to our post '16 estimates of the result by group

Nationwide, this yields the following result:
Biden+10, 54-44
Whites 46-52
...col+ 59-39
...no col 37-61
Black 90-9
Hispanic 63-35
plausible enough for illustrative purposes

By state, these estimates yield results that look a lot like recent polls (though keep in mind that, unlike this simulation, national shifts would undoubtedly manifest in non-uniform and unpredictable ways by state):
MI Biden+10
WI +10
PA +9
FL +6
NC +6
AZ +4

The next-tier of states also looks quite a bit like state polls, though the Democratic weakness among Hispanic voters in national polls (which I'm not sure I expect to last and may not materialize in TX) barely blocks blue TX
ME-2 Biden+2
OH +2
IA +1
GA +1
TX Trump+1

All of this shouldn't be too surprising. More surprising is what comes next:
AK Trump+4
UT Trump+5
SC Trump+7
MT Trump+7
KS Trump+8
MO/IN Trump+9

As cautioned earlier, individual states will defy national trends in significant ways, esp weird ones like AK/UT.
But this creates risk for the GOP: it wouldn't take much more for a few to be really competitive, even if, for the same reasons, one or two might remain solid Trump

Obviously it doesn't matter too much whether Biden flips AK or something. But it may matter a lot downballot: four of those states feature plausibly competitive Senate races, and extra Senate flips would matter a lot for Democrats.

As an aside, the 2022 Senate map does not feature many competitive Democratic-held races, and if Dems could get to 53+ seats they'd have a very serious path to hold the Senate through 2024 and a hypothetical midterm wave

The consequences for the GOP in the House might be equally alarming, as Biden carries more than 250 congressional districts in this scenario
At this point, Biden gains among white voters really do reach, if barely, the 'busted gerrymander' point in OH/TX/MI.

Biden wins several of the Trump +10 or more districts that keep popping up in private polls, like IN05, MO02, TX21, etc.
But he also wins districts that aren't getting much attention, perhaps because they're not overly heavy on college grads, like AZ06, OH10, MI06, FL16

Of course, the 'national trends may not manifest uniformly point' is particularly true by district. It wouldn't be hard to imagine, hypothetically, Biden winning an IN05 by 7 without flipping FL16. Real world election results always defy simple demographics

But the idea that GOP losses might now well past '18 shouldn't be a surprise: Trump's approval rating today is a net-6 points lower than it was heading into the midterm.