Re brexit, it will be interesting to see what influence Bbiden will have
He's already having it. There is no way the Uks complete capitulation on the IMB wasn't because Boris knew he couldn't meet Biden until it was history.
That's before you consider that Biden has clearly indicated he has zero time for Boris anyway.
And regardless of how Brexit finally falls (apart) any UK Prime Minister is going to have to meet a POTUS who has been briefed - since 2016 - that Brexit harms the US. There's no way around it.
The interesting thing UK-wise is that Boris is still in thrall to a bunch of ERGers who haven't yet got the memo that there's nothing in the US for them now - not until 2024 at the earliest.
I can actually imagine US encouragement for Irish unification too. Just to stick it to the Brexiteers.