look at this:
Please note that as of June 17, 2002, the Consular Section of the American Embassy in Ottawa will accept applications for non-immigrant visas only from persons who have made appointments. Persons coming to the Embassy to apply for a visa without an appointment will not be admitted, but will be provided information about how to make an appointment.
看来只好预约,多伦多是可以直接去排队的。