Trump's mother became a NATURALIZED AMERICAN CITIZEN four years before Donald was born. She did NOT attain citizenship by marrying Trump's father. And in becoming a citizen, she had to renounce her allegiance to the King, renounce he UK citizenship, taking an oath of allegiance to THIS NATION!
Trump was born to TWO American citizens on American soil and does NOT have dual citizenship.
These are the facts that you ignore:
Some might argue that Mary Trump’s US citizenship ceremony of March 10, 1942 would have sufficed to accomplish that. Those making this argument would be wrong as a matter of law.
A person may renounce British nationality by making a specific renunciation to the Home Secretary. Renunciations made to other authorities (such as the general renunciation made as part of the US naturalization ceremony) are not recognized by the UK.