Question: when did the united states officially become a country
[{'answer': '1776', 'provenance': [{'wikipedia_id': '63876', 'title': 'History of the United States', 'start_paragraph_id': 2, 'start_character': 33, 'end_paragraph_id': 2, 'end_character': 37, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '63876', 'title': 'History of the United States', 'start_paragraph_id': 73, 'start_character': 0, 'end_paragraph_id': 73, 'end_character': 485, 'bleu_score': 0.9304844600065421, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4128954163282493644}, 'section': 'Section::::American Revolution.\n'}]}]