What the Senator said about it only being for new citizens is not accurate. The proposed legislation, as it reads in the current draft:
SECTION 1. Short title.
This Act may be cited as the “Exclusive Citizenship Act of 2025”.
SEC. 2. Findings.
Congress makes the following findings:
(1) To preserve the integrity of national citizenship, allegiance to the United States must be undivided.
(2) Existing law allows certain United States citizens to maintain foreign citizenship, which may create conflicts of interest and divided loyalties.
(3) It is in the national interest of the United States to ensure that United States citizenship is held exclusively.
SEC. 3. Definitions.
In this Act:
(1) IN GENERAL.—Except as otherwise specifically provided, any term used in this Act that is used in the immigration laws shall have the meaning given such term in the immigration laws.
(2) FOREIGN CITIZENSHIP.—The term “foreign citizenship” means any status recognized by the government of a foreign country that confers on an individual the nationality or citizenship of such country or requires the allegiance of an individual to such country.
(3) IMMIGRATION LAWS.—The term “immigration laws” has the meaning given such term in section 101(a) of the Immigration and Nationality Act (8 U.S.C. 1101(a)).
SEC. 4. Prohibition on dual or multiple citizenship.
(a) In general.—
An individual may not be a citizen or national of the United States while simultaneously possessing any foreign citizenship.(b) Effect of acquisition of foreign citizenship.—A citizen of the United States who,
after the date of the enactment of this Act, voluntarily acquires foreign citizenship shall be deemed to have relinquished United States citizenship.(c) Dual citizens.—
(1) IN GENERAL.—
Not later than 1 year after the date of the enactment of this Act, a citizen of the United States who also possesses foreign citizenship shall—
(A) submit to the Secretary of State a written renunciation of such foreign citizenship; or
(B) submit to the Secretary of Homeland Security a written renunciation of United States citizenship.
(2) EFFECT OF NONCOMPLIANCE.—An individual subject to paragraph (1) who fails to timely comply with that paragraph shall be deemed to have voluntarily relinquished United States citizenship for purposes of section 349(a) of the Immigration and Nationality Act (8 U.S.C. 1481(a)).
(d) Effective date.—This section shall take effect on the date that is 180 days after the date of the enactment of this Act.
SEC. 5. Administration and enforcement.
Not later than 180 days after the date of the enactment of this Act—
(1) the Secretary of State shall—
(A) promulgate regulations to carry out this Act, including procedures for declaration, verification, and recordkeeping of exclusive citizenship; and
(B) coordinate with the Attorney General and the Secretary of Homeland Security to ensure that any individual deemed to have relinquished citizenship under this Act is appropriately recorded in Federal systems and treated as an alien for purposes of the immigration laws; and
(2) the Secretary of Homeland Security shall publish in the Federal Register a notification of the requirement under section 4(c).
I don't see this passing, as too many people have too much interest in keeping their dual citizenships. If by some stretch it did pass, it'd be tied up in court for a very long time. Here's a write-up from the National Law Review about it:
https://natlawreview.com/article/american-citizens-and-nothing-else-what-exclusive-citizenship-act-2025-would-do-and