While the British still keep their copies of the Enigma intercepts a secret, a US Freedom of Information suit forced the US to declassify the American copies. It is very clear that both the American and British government were fully informed of the holocaust as it was happening, at least on the highest level. This is in addition to other intelligence the Allies received.
So if we want someone to boycott because of the holocaust, start with the United States and the self-governing (during the early 1940s, meaning Canada and Australia as well as Great Britain) portion of the British Empire.