A Reddit user wrote that an "Anglophile friend" resorted to writing to Buckingham Palace because he was "frustrated with the current field of presidential candidates (particularly on the GOP side)".
The letter was addressed to both the Queen and Prime Minister David Cameron.
"On behalf of the American people, I urgently implore you to take us back," the letter read.
"Clearly, the options we have to lead us aren't up to par. Again, please, I beg of you, make the United States of America a colony of the United Kingdom. For further reasons as to why this is such a necessary, albeit drastic, step, I refer to tonight's Republican Party Primary debate. Thank you. God save The Queen," the letter was quoted as saying by The Independent.
The letter was sent on September 16, when 11 front-runners for the Republican Presidential nomination had gone head-to-head for three hours on CNN.
Sharing a photo of the reply, which appeared to be on official royal letter paper, the person wrote that they were shocked his friend was dignified with a response.
The Queen's deputy correspondence coordinator wrote, "I have been asked to write in response to your recent letter to The Queen in which you express your views about the American government."
"Whilst your views have been noted, you will appreciate, I am sure, that there can be no question of The Queen intervening in the affairs of another Sovereign state," it said.
Buckingham Palace has become known for its correspondence, with one of the Queen's aides replying to a six-year-old girl who invited the monarch to her birthday party earlier this year.
The response said the Queen "greatly appreciated the thought and hopes you have a lovely time".
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