I am currently in Canada with work permit. My work requires me to visit US frequently and I have been there multiple times. Recently my Canadian Visa has expired I need to visit US again. Can I visit US with my expired Canadian visa and come back to Canada?
Yes, you are allowed to travel to Canada using a valid work (or student) permit instead of a visa, provided you have only gone to the USA or St. Pierre and Miquelon.
Timatic (the database which airlines use to verify that your travel documents are sufficient for travel) states, in relevant part:
Passengers with a valid student or work permit are allowed to return to Canada from the USA or St. Pierre and Miquelon without obtaining a new visa, if they have not left the USA or St. Pierre and Miquelon to a third country and are returning within the period of entry authorized (expiry date of student or work permit) or within 6 months of original entry stamp.