Question: Which debut album has sold over half a million copies in the United States and is by an American alternative rock band that released its first digital debut EP on May 2010 of a different album?
{'answer': 'Megalithic Symphony', 'supporting_facts': [['Back from Earth', 0], ['Back from Earth', 1], ['Back from Earth', 2], ['Megalithic Symphony', 0], ['Megalithic Symphony', 3]]}