I am a foreign student with a Canadian Resident Permit. I intend to travel back to my country for a holiday and will come back to Canada to pursue my study. My flight to my country (Zambia) is through Seattle in the USA where I need to change plane. Do I need a US visa to transit even though I am not getting out of the airport?
Yes, you need a transit visa, because the US does not have sterile transit facilities at any airport.
I would recommend flying directly from Canada to Europe and connecting there instead. Because you have a Canadian visa, if you have a direct connection, you will not need a transit visa for the UK or the EU (Schengen).