I had no idea until my brother sent me this:
(We in fact had opossums and raccoons fighting for our trash)
Well yes, but opossums are traditionally called possums here in the US.
I know that article in the link is entitled Raccoons vs Opossums, but despite the adversarial title, I still don’t see the Great Debate in the OP.
Yes, I knew that, but in the US we still mostly call them 'possums. Back in CA, I had problems with a mama possum that discovered the cat’s food dish, then later one of her kids got inside the house and decided to stay there for awhile 'til I finally managed to catch it. The adults are usually slow and lethargic mostly, but the babies can speed around like a little rat.
Given that the word ‘possum’ was originally applied to the American beast - as a shortening of ‘opossum’, which is derived from an Algonquin word - then applied to the Australian one due to its resemblance to the former, I would dispute the idea that ‘possum’ is not a synonym for ‘opossum’.
'possum? That’s an odd name. I’d have called them chazzwozzers.
“Raccoons on the other hand are not related to either but are more closely related to bears.” That’s a bit overstated, isn’t it. It’s one theory, but most eutherian animals are more closely related to each other than to marsupials or monotremes.
Opossums bother a lot of people but they’re pretty harmless. I was chased to the car by a gang of raccoons in suburban Pittsburg, California in the middle of the night.
Moved from Great Debates to MPSIMS.
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Opossum vs Possum
Which is the one that looks like mean drunk Jamie Kennedy after a bad night at a comedy club?
The Irish one.
Chrome won’t let me open your link (“This site can’t provide a secure connection”). But here’s another site on the difference between opossums and possums:
Well…yes, and no. You’re right that any two Placental mammals will be more related to each other than to Marsupials, but even within the Placentals, raccoons are closer to bears than most - not the closest, but close. (Weasels are siblings, seals are cousins, bears are uncles.) Though, honestly, the fact that it’s not particularly overstated is what makes it a weak comparison in this case.
‘Closer to humans’ would have been a better comparison, I think.
My dad used to have a sticker on the '73 Thunderbird that read, “Eat Mo Possum”.
I’m sure it meant something to him.
I just this week found out the the robins we have in America are a different bird than the robins that live in Europe. They’re completely different species that just happen to have similar coloring. So when the early English settlers came to America they named the American birds after the ones they knew from back in England.
We used to have both opossums and raccoons around here, but haven’t seen a 'possum in ages. The raccoons have pretty much taken over, it seems. The raccoon is a more attractive critter than the 'possum, but it can sure be a nuisance.
I feel rather stupid for having been aware that there were similar though not identical animals in the Americas, and Australia, called opossums in both places; but not having taken any thought as to where the name came from. It now seems blindingly obvious -– English-speakers moving across the Atlantic into North America, encountering marsupials for the first time in the shape of the American creature, and borrowing a Native American name for it; and later – doing a similar exercise re Australia –- applying the name “opossum” to the pretty-much-alike beast native to that region.
It occurred to me to wonder what the Spaniards –- encroaching into South and Central America at about the same time as the British further north –- made of opossums. Looking up the Spanish word for the animal, I found zarigüeya (happened to know the French word for it, sarigue –- thus similar). Wonder now, whether that word is a corruption of a Native American one from those parts of the Americas. (Nava can usually be relied on to know about, and inform people concerning, this sort of thing.)
For the record, in Australia we call them possums, not opossums.
And they’re not the ugly critters you Yanks have…ours are quite a delight (unless you get them cantering over your galv iron roof in the dead of night, or fighting out a territorial battle in your leptospermum tree outside your bedroom window). 
We have two possum-types:
The Brushie and my favourite, the Ringtail.
And neither of them hang by trees from their tails.
Though in my neck of the woods, a lot of them hang from electric wires by their cold dead little paws…
But are they not, zoologically-officially, correctly titled “opossums” – although in ordinary discourse, people virtually always say / write “possums”?
Yes. The little buggers are a serious pest in New Zealand and are regularly trapped. They’re native to Australia and protected here, though, but because of the former my instinct is dislike.
Why, thank you 
but I crib mercilessly from RAE. In this case they’ve failed us: all they can say is that the word comes “from Brazilian Portuguese çarigueia”. Anybody have a good reference for Portuguese word origins handy?