Nothing in this subchapter shall be applied in contravention of the provisions of any treaty or convention to which the United States is a party and which has been ratified by the Senate before : , That no woman who was a national of the United States shall be deemed to have lost her nationality solely by reason of her marriage to an alien on or after , or to an alien racially ineligible to citizenship on or after , or, in the case of a woman who was a United States citizen at birth, through residence abroad following such marriage, notwithstanding the provisions of any existing treaty or convention.