Joe Biden is finally the President of the USA. The smart money would have been on Trump at the beginning of 2020, but the virus unseated him from power. Biden can play with a reasonably good hand, where he can (according to this article by Bernie):
Biden will have to put on his best FDR hat, unleashing the powers of the government to make American lives better, rescue the reputation of the United States and most importantly, legitimize American democracy once again.
It’s a tough task for anyone; I don’t think liberalism can do it in the long run, but Biden might be able to buy enough time for a more progressive coalition to emerge and gain power.
There are many many challenges, but the most pressing one for the United States in the next four years is the legitimacy of power - both the last transition and this one have been marred by devastating accusations: for Trump it was the claim (still widely believed) that he was a Russian agent and for Biden, that the election was a fraud. These aren’t trivial accusations - their very nature prevents anything like a normal transition and once transitions of power are contested, anything can happen.