The USA will accept a RAT covid test result for entry, and so will Portugal and Italy. But not all destinations will accept a rapid antigen covid-19 test result. So check with a reliable source, such as the Government of Canada’s Travel Advisories. Your travel agent or airline may also be able to advise, or you could check the embassy for your destination country. Governments have been changing entry requirements rapidly and without notice, so you should check this information at each stage of your travel planning, right up until your departure.