In the US and Canada, what are the rules on portable appliance testing?

[pattesting1]

I'm curious because one of my duties at work is PAT testing. In the UK, probably all of the EU too, class 1 appliances have to have an earth test. However, to do an earth test on appliances imported from the US or Canada is often nearly impossible or impossible without destroying the appliance. Do US states and Canadian provinces require regular safety checks on electrical appliances? Typically, I'm testing scientific equipment in chemistry laboratories but appliances in any public place need to be tested, so, for example, TVs and table lamps should be tested in hotels. They are given a tag to state they've passed, which is stuck somewhere inconspicuous. The question is really about health and safety regulations.