CREATE TABLE table_37733 ("Name" TEXT, "Birth date" TEXT, "Age as of 1 February 2014" TEXT, "Province or Country of birth" TEXT, "Province of residence" TEXT)

What is the average age as of February 1, 2014 for the supercentenarians born in the United States?
SELECT "Age as of 1 February 2014" FROM table_37733 WHERE "Province or Country of birth" = 'united states'
SELECT "Age as of 1 February 2014" FROM "table_37733" WHERE "Province or Country of birth" = 'united states'