Marijuana’s effects last about one to three hours. A bit longer if ingested. There might technically be longer-term effects noticeable in a clinical setting, but nothing to a degree that would impact somebody’s ability to function at a typical level.

To my understanding "being tired" (which is absolutely part of being hungover the next day after a night of heavy drinking) is comparable and according to some sources pretty much equivalent to being "under the influence" in terms of how much it can impair you when operating heavy machinery.

You did NOT remember correctly. The only way you're going to have effects for a week is by using it for a week! The effects are VERY predictable, as studies have shown first-hand through trials for many decades. The only thing that isn't absolutely certain is an individual's rate of processing THC-COOH, which is only a leftover metabolite of what was once psychoactive THC (THC-A). You will absolutely test positive for THC-COOH a week after a single usage, sometimes up to a month; because it's stored in your fat. For this reason, it can even be detected up for multiple months in heavy users! An inactive metabolite is unable to cause any psychoactive effects.

Mouth swabs are a more reasonably analog to breathalyzers for cannabis, although even with those the detection period can be up to 48-72 hours. But still, much better than the months long detection period for the more common urine tests.

My hope is once its legalized fully, more effort can be put into researching and designing more sensitive tests until we have something that is equally as capable as breathalyzers are(which is questionable in and of itself, but I'll settle for equal treatment under the law for now rather than aiming for perfection).

cannabis tests check 30 days, not 8 hours. Hangovers can happen past 8 hours as well. Balls in your court, w0de0.