Emma DeSouza, from Magherafelt, lodged a challenge in the Court of Appeal in Belfast in November, following a ruling that those born in the north are automatically British citizens.
She won a case against the Home Office in 2017, after it deemed she was British, when her US-born husband Jake applied for a residence card.
But in October an immigration tribunal upheld an appeal brought by the Home Office.
Government lawyers argued that people born in Northern Ireland are British citizens according to the 1981 British Nationality Act, even if they identify as Irish.
The Good Friday Agreement allows people to identify as British, Irish or both, but the Home Office says the agreement did not supersede the 1981 British Nationality Act.
Ms De Souza is set to visit Washington, Philadelphia, New York and Boston over a 10-day period from Sunday.
She said she intends to seek support to put pressure on the British government to change its nationality laws.
“The UK government has failed to give domestic legal effect to a key provision of the Good Friday Agreement,” said Emma.
“Instead of addressing this implementation gap it is seeking to rewrite the intent and scope of the provision and continues to challenge the purpose of this provision through the British courts.
“The Good Friday Agreement gives the people of Northern Ireland an explicit right to identify and be accepted as Irish or British or both, as they so choose.
“The British government’s position is out of step with this commitment and its nationality laws are inconsistent with both the letter and the spirit of the Good Friday Agreement.
“Fundamental change is required and political pressure must be brought to bear on the British government.
“The majority of Northern Ireland’s political parties and the Irish government agree that legislative changes to the UK’s nationality laws are required.
“It is my hope that added political pressure will bring the British government to the table.”