Australia isn't too bad, you got more chance of being killed by a car than killed by a native animal.
Our red back spider is very similar in appearance to your black widow spider, and even tho they are poisonous, they usually have a small web in the corner somewhere and don't bite unless you try to grab them.
Funnel web spiders are dangerous but it is mainly the males that bite people because they wander about looking for mates. Funnel webs are only found on the east coast of Australia.
White tail spiders are dangerous because they wander around your house at night and they have a flesh eating bacteria on their fangs. They regularly crawl into beds and bite people. You wake up the following day with red lumps on your hands or fingers and a few weeks later the skin and muscle starts dissolving. Anti-biotics or raw honey can kill the bacteria but it's a bit scary.
Male kangaroos kick crap out of you with their back legs and they can rip you apart, but most roos take off as soon as they see people, coz people shoot them and run them down.
Male Platypus have venomous spines on their back legs but unless you grab one, it won't harm you. And they are pretty secretive so most people never see them, let alone get close enough to grab one.
Dingos are a type of wild dog only found in remote areas. They are normally shy and don't hassle adults but they will take babies if they are hungry. Having said that, I think 2 babies have been killed by dingos in 50 years, so they are nothing to worry about. Pet dingos make really nice pets.
Flying foxes (aka: fruit bats) live in Queensland and across the top of Australia, and can carry a virus from horses. If people catch the virus, there is a strong possibility they will die from the virus. The virus is spread through bat poop and it can land on fruit. People touch the fruit, get sick and die a few days later.
Blue ring octopus are found in rock pools and along the coast. They are tiny and rarely seen. Their numbers have diminished due to pollution. They are extremely poisonous and if you touch one with your bare hands, you can get poisoned with a toxin that causes paralysis. 10 minutes later your heart stops and you fall down dead. However, if someone finds you and gives you CPR and EAR, or puts you on life support, the poison breaks down over a couple of hours and you wake up.
Box jellyfish can kill you with the stingers on their tentacles. They are found in Queensland around the Great Barrier Reef. If you wear a stinger suit or wet suit, you are fine but bare skin can leave you susceptible to stings.
Most of the snakes in Australia are venomous and quite a few are dangerous because they attack and bite repeatedly. The taipan is the worst and there are different species found on the east coast, up north and in the desert. They are lethal and if you get bitten and don't get help straight away, you will die. There are rabbits (like Bugs Bunny) up in Queensland that actually hunt down taipans and kill them. Tiger snakes are found in the southern half of the country and while they are venomous, they aren't that aggressive and try to move away when people approach them. Sometimes they have a bad day and will rear up and strike at people so you give them space and they are fine. Most other snakes are venomous but prefer to avoid people.
Saltwater crocodiles scare the hell out of me and extremely dangerous. They are found in fresh and salt water along the top of Australia. You don't go in the water up there and if fishing, you stay several meters away from the edge and never go near water unless you can see into it.
You lot get to play with bears, wolves and pumas. I will stay in Australia, it's safer than playing with them.