The major concern is that the economy can't roar any more - or not like we got used to long in the past.
In the postwar era ~1945-1975, the USA had average annual GDP growth approaching 4%, with average (mean) incomes rising about 2.5% annually. But it has been slowing since 1980 and now perhaps an average of 2-2.5% annual GDP growth might be good, with wage increases correspondingly lower. Trump promised postwar-style growth from his tax cuts and fell far, far short. His stimulus was little more than a short, slight bump. Lower growth is the probably the new normal, reluctant as many may be to accept it.
Possibly, the economy simply cannot generate that postwar growth, either 1) at all (because the technological advancements that underpin it cannot be generated fast enough) or 2) without massive reforms of the economy. In the case of (2) neither Trump nor Biden nor the majority of their parties could even find the ballpark on the map in terms of contemplating those sorts of reforms. The big options on the fringes are either the progressive Green New Deal or libertarian tax and regulation bonfire.
There is no chance that Biden is going to go back to the old, cosy, US-China relationship. China is showing its teeth, overtly challenging the USA and threatening its allies. The USA must reduce its reliance on and resist China as a national security requirement. I'm sure Biden will try to soothe the current ill-will somewhat, but in reality the USA and China are at this point almost certainly fated to create stronger boundaries.