Outside of any swing states/battlegrounds here are some possibilities from west to east:
Alaska-Biden did decent in 2020, and Obama made gains there in 2012.
Hawaii-Incumbents tend to do better than expected.
Utah-State is trending blue, and Trump is a really bad fit there. Biden could possibly crack 40% there.
Colorado-Trending blue as well, and even Bennet did better than Biden 2020. This might be the most likely state on the list for Biden to improve in.
Kansas-Also trending blue, and Biden will probably improve there a little from 2020 due to the trend in Johnson county.
Arkansas-Has been getting redder every election for decades now, but it looks like Rs are close to their ceiling here. It's possible Trump stalls out and Biden manages to get a really small swing here towards him.
Kentucky/West Virginia-Its unclear whether or not Trump is maxed out in Appalachia or not. Even if he isn't the shifts in some of the suburban Kentucky counties might swing the state towards Biden again. In WV he's at risk of losing Monongalia county.
Virginia-It's unclear how much Biden is maxed out in NoVA suburbs and the cities. If he can get another few points from them its possible he improves in the Old Dominion.
Delaware-It's his home state, and its very possible he improves there.
Largely agree with this list but disagree with AR; Dems have not bottomed out in AR yet, especially if you look at how many rural white northern AR rurals actually vote to the *left* of Missouri rurals to the north even once you account for any scattered black population.
The reason it swung right in 2020 wasn't really because Biden did particularly bad in the state but moreso because Clinton did well; in hindsight it's clear in 2016 Clinton got a modest boost in much of rural AR.
