They're about the same size: the UK map blocks are 1 km x 1 km US: "the United States consists of 11,078,300 Census Blocks." The USA area is 9.834 million km

They're about the same size: the UK map blocks are 1 km x 1 km US: "the United States consists of 11,078,300 Census Blocks." The USA area is 9.834 million km², according to a well-known search engine. So about .9 km² in average, roughly in line with "Of them, 4,871,270 blocks totaling 4.61 million square kilometers were reported to have no population living inside them".