Democratic congressman Dan Kildee urged Foreign Secretary Liz Truss to have face-to-face negotiations with Brussels.
The group met Irish premier Micheál Martin on Monday in Dublin, and will later visit Northern Ireland.
But the DUP said their view of the protocol was “one-sided”.
On Monday, Mr Martin said there was “a deep well of support” for a “joint, pragmatic solution” to concerns over the protocol.
He was speaking alongside Prime Minister of the Netherlands, Mark Rutte, who said the EU had “shown maximum flexibility” in negotiations.
A nine-strong team led by Congressman Richard Neal is visiting to discuss the post-Brexit trading arrangements.
Mr Kildee, who met Ms Truss over the weekend, said there was no indication the UK Government intends to “change course”.
“It’s important, and we stress this, that the (UK Government) negotiate and that they not take unilateral action,” Mr Kildee told RTE Morning Ireland.
“The only way we can come to agreement, the only way we protect the incredible progress that’s represented with the Good Friday Agreement, is face-to-face negotiation.
“We think unilateral solutions will not work, face-to-face negotiation to work out some of these technical questions can be achieved.”
Speaking in Kerry on Sunday, Mr Neal said the US would be “unwavering” in its support of the Good Friday Agreement.
But the DUP says the protocol will destroy the agreement.
Economy Minister Mr Lyons said it was “not going to be an easy task” to explain that view to the US delegation.
But speaking on BBC News NI’s Good Morning Ulster programme on Monday, Mr Lyons said his party would be very clear when it meets with the US team, that “rather than protecting the Good Friday Agreement and its successor agreements, the protocol actually damages them”.
“It is not going to be an easy task,” Mr Lyons said.
“I previously met with Congressman Neal in Washington and reminded him and [House of Representatives Speaker] Nancy Pelosi of the problems with the protocol.
“It is fair to say they weren’t interested and we’re going to have a particular challenge with Congressman Neal.”
Mr Lyons said Mr Neal was a supporter of Irish unification and that he had worked closely with Friends of Sinn Féin.
“So yet again we’re dealing with more American politicians who are one sided and that adds to the challenges too,” he added.
Mr Lyons said his party wanted to see movement on the protocol but also accused the EU of being “painfully slow” at recognising issues surrounding the post-Brexit trading mechanism.
The protocol is a special arrangement that keeps Northern Ireland aligned with the EU single market for goods, avoiding a hard border with the Republic of Ireland.
The arrangement ensured free trade could continue across the Irish land border, which is a sensitive issue because of the history of conflict in Northern Ireland.
But it brought in some new checks on goods moving between Great Britain and Northern Ireland and has been criticised by unionist politicians since its introduction in 2021.
They say it has undermined Northern Ireland’s place in the UK and that it has led to increased costs for consumers.
Sinn Féin leader Mary Lou McDonald met Mr Neal in Dublin on Monday.
Following the meeting, Ms McDonald tweeted: “The USA stands resolute in defence of the Good Friday Agreement and the protocol. It is imperative that the executive is formed. No delay.”
On a visit to County Kerry in the Republic of Ireland on Sunday, Mr Neal described the United States as a “guarantor of the Good Friday Agreement”.
“The Good Friday Agreement has worked, and it’s worked quite well,” he said.
Ms Truss announced on Tuesday that new legislation would be introduced to change the protocol.