"Up arrow, Up arrow, Down arrow, Down arrow, Left arrow, Right arrow, Left arrow, Right arrow, 'b', 'a'", inside or outside of the input field, does nothing.
It does work, but only on https://america.gov/chat (i.e., after sending a message first), not the front page. Also, note that the Konami Code actually ends with "Start".
Did it on that page the way I said, did it the way I said + "start", did it without the "b" and "a" and just start - still nothing.
You need to send a message first, otherwise https://america.gov/chat just redirects you to the front page.