The US Government doesn't recognize the junta in Myanmar, and still refers to the nation as Burma.
From the CIA World Factbook: Since 1989 the military authorities in Burma have promoted the name Myanmar as a conventional name for their state; the US Government did not adopt the name, which is a derivative of the Burmese short-form name Myanma Naingngandaw
True enough, but when hosting an ASEAN summit, we should probably go with ASEAN protocol, which does recognize 'Myanmar' as the country's name.