Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_18 (round INTEGER, nationality VARCHAR, position VARCHAR)
### Question:
What is the average round of the rw position player from the United States?
### Answer:
SELECT AVG(round) FROM table_name_18 WHERE nationality = "united states" AND position = "rw"