[quote author=Wendy]If you are working for a Canadian company, being paid in Canadian dollars deposited in a Canadian bank, and are visiting this country...[/quote]
That would appear to be the OP's case, although I didn't realize that on first reading. Bottom line is that, provided he's not 'employed' in the U.S., he'll be fine. Been there done that (legally) for an extended time.
... aren't a permanent US resident ....
Wrong term; In my first response I linked to IRS Publication 519, U.S. Tax Guide for aliens (includes resident and non-resident aliens, both of which require the paying of taxes if working in the U.S.). 'Resident alien' and 'green card holder' are equivalent terms used for a 'permanent resident', but folks do not need to be permanent residents (or resident aliens or green card holders) to legally work and pay taxes in the U.S.
When we talk about resident/non-resident aliens, immigrant and non-immigrant status, they're determined by the US Citizenship and Immigration Service (previously the INS, Immigration and Naturalization Service). Each status has it's own process that must be followed. The previously linked UCSIS web site spells much of this stuff out.
IOW residency and immigration status are defined/controlled by a different agency than the IRS, so both must be researched together. I've been around both loops numerous times, personally and for family members and employees, with and without legal (immigration attorneys) and tax pro help, and have lots of horror stories for each scenario.
Good luck with your research. If I can share the benefit of having been in various residence/immigrant states and various tax statuses, let me know.