Its removal back in 2009 caused some comment in the American press including this:
Obama removed the bust of former British Prime Minister Churchill shortly after moving into the White House, replacing it with one of former U.S. President Abraham Lincoln. The Times of London, England’s largest newspaper, wrote on Jan. 31, 2009, “Mr. Obama shows little evidence of the Anglophilia that led his predecessors to pepper speeches with quotations from Churchill. Instead, there have been suggestions that he has reason to disdain the former Prime Minister. In 1952 Churchill declared the Kenya emergency in the homeland of Mr Obama’s father, sending in troops to crush the Mau Mau rebellion against colonial rule. Among the Kenyans who were detained without trial and allegedly tortured by the British was Hussein Onyango Obama, the President’s grandfather.”
Another contemporary press report at the time says the bust was "On loan from the Government's (UK) art collection:
A bust of the former prime minister once voted the greatest Briton in history, which was loaned to George W Bush from the Government’s art collection after the September 11 attacks, has now been formally handed back. The bronze by Sir Jacob Epstein, worth hundreds of thousands of pounds if it were ever sold on the open market, enjoyed pride of place in the Oval Office during President Bush’s tenure. But when British officials offered to let Mr Obama to hang onto the bust for a further four years, the White House said: “Thanks, but no thanks.”