I'm from Algeria, and I plan to visit Canada (Montréal) for 20 days next november as a tourist (me and my mom ), and then I want to visit USA (Mississippi) for one week (alone). can anyone please help telling me what the procedures would be, Like is there any visa so I can visit both or should I request for each one separately. and if so, should I request for the US visa from Algeria or can I have it at the Canada/USA border ?
As they are separate countries, you will indeed need two visas - one for Canada, and one for the US. You will need to apply for each one separately.
As Algeria is NOT one of the countries eligible for the US Visa Waiver Program, you'll need to apply for a visa in advance - it's not possible for you to get one at the border.
To get a visa, you'll need to fill out an application from the Canadian embassy in Algeria for Canada, and the US Embassy for the United States visa. These quite often take time to process, so try and do it as soon as you know when you're travelling - don't leave them to the last minute!