President Joe Biden maintains “unequivocal” support for the Belfast Agreement, a White House spokeswoman said.
The 1998 deal, which largely brought an end to the Troubles, also enshrined cooperation with the Republic.
Foreign Affairs Minister Simon Coveney has said the UK cannot be trusted over the Northern Ireland Protocol, which ensures trade across the border remains open and free-flowing.
White House press secretary Jen Psaki said, “President Biden has been unequivocal about his support for the Good Friday Agreement.”
“It has been the bedrock of peace, stability and prosperity for all the people of Northern Ireland.”
The UK has unilaterally extended some grace periods of light-touch regulation on goods crossing the Irish Sea to Northern Ireland following lobbying by businesses.