He said the opening of the embassy was a matter for the USA government.
Mr Trump claimed he had cancelled his trip the trip because he was unhappy that the embassy had been moved from Mayfair to Nine Elms in south west London.
Prime Minister Theresa May was the first foreign leader to visit Trump after his inauguration in January previous year, and they were filmed emerging from the White House holding hands.
Trump said he had cancelled next month's visit, which had been set to include the opening of the new USA embassy in London, because he did not like the building and thought it was a "bad deal" financially.More news: Murphy Capital Management Inc. Acquires 2460 Shares of Starbucks Co. (SBUX)
While Trump blamed the embassy real estate deal for his decision not to visit the capital of one of the United States' closest allies, various reports indicate planned protests contributed to the decision.
But British officials have been dismayed by some of Trump's pronouncements, particularly a proposed ban on Muslims entering the United States and most recently when Trump rebuked May on Twitter after she criticized him for retweeting British far-right anti-Islam videos. "Bad deal. Wanted me to cut ribbon-NO!"
Khan noted Trump's cancellation "reinforces what a mistake it was for Theresa May to rush and extend an invitation of a state visit in the first place".
"It seems he's finally got the message". He said the opening of the embassy was a matter for the U.S. government.More news: Is PNC Financial's Q4 Earnings Beat Good Enough?
Many British politicians have voiced their opposition to Trump being granted a state visit, and say the invite should be recalled.
The US flag was lowered for the final time on Tuesday from the top of the former 600-room embassy in Grosvenor Square, where US General Dwight Eisenhower had his headquarters during World War Two.
"It appears that President Trump got the message from the many Londoners who love and admire America and Americans but find his policies and actions the poor opposite of our city's values of inclusion, diversity and tolerance", Khan said.
"I think we have to welcome the American President to Britain", Johnson said.More news: 100th satellite launch a landmark: Rajnath Singh
In response to the cancellation, London Mayor Sadiq Khan celebrated the news, saying the US president "is not welcome here".