The pair held their first bilateral meeting at the fringes of the United Nations summit in New York after Ms Truss caused controversy by failing to say whether the ally was “friend or foe”.
In a message on Twitter, Mr Biden said: “I am sick and tired of trickle-down economics. It has never worked.
"I predicted that opinion on rejoining would move slowly and remorselessly, by demographic replacement rather than Brexiters seeing the light, but I can feel it happening much faster than that now."
Those who live and work in the low-tax areas envisaged by the Prime Minister could see their own contributions cut, it is understood.
A report published in January found the effects of lowering tax has an economic effect that is "statistically indistinguishable from zero”.
It comes as the EU have announced they will impose a windfall tax electricity-producing companies that are making extraordinary profits thanks to the war in Ukraine and climate change.
"You told me this morning when I was in here... that you would drink this water," he says to the commission. "So, would you drink it?"
Gina Miller tweeted:Why is Liz Truss going on the Royal Tour? How much will it cost taxpayers? 'While she is not required to be present, she believes it is important to be present.'
"Make no mistake, the plan is to turn the UK into the sweatshop of Europe," wrote one person after watching the clip.