When applying for your visa, you need to be prepared for possible delays for various reasons. Unfortunately, there is very little that can be done to speed up the process due to security background checks. Furthermore, in some countries you might have a wait to get an appointment. It is always a good idea to start out by checking the website for the U.S. Consulate in the city where you plan to apply for your visa.
Special Rules for Traveling to Canada
It is possible to travel to Canada with an expired U.S. visa if your purpose for that visit is for pleasure (tourism) and the visit is for less than 30 days. This is a special travel agreement between the U.S. and Canada for students studying in the U.S. called "automatic revalidation." Depending on your country of citizenship, you may need to apply for a Canadian visitor visa.
If you wish to apply for a new visa from a U.S. Consulate in Canada, you must schedule an appointment. You should note that if your application for a new visa from a U.S. Consulate in Canada or Mexico is denied, you must return to your country of residence and apply for the visa from there. Automatic revalidation is not possible if you start the process for getting a new visa in Canada.
The rule regarding automatic revalidation of an expired visa for the purpose of re-entry from Canada does not apply to nationals of the following countries: Iraq, Iran, Syria, Libya, Sudan, North Korea, and Cuba.
Similar regulations apply when traveling to Mexico.