If you’re flying to the US, make sure to have a Covid-19 test done by the day before departure at the latest, or you risk being denied boarding.
US President Joe Biden has changed the policy for all incoming flights into the United States starting Dec.6 2021. Anyone arriving to the USA by air must have had a Covid-19 test no later than 24 hours before departure. This has changed from the 72-hour test window that was in place before.
Canada has however lifted strict rules for incoming US tourists. Right now all other incoming air travellers need to be tested and isolate until the results come back.
These rules only apply to people going to the US by plane. If travelling across a land border, only a proof of vaccination will be required for border agents.