There are a lot of different salmonella species.  Some cause
life-threatening diseases like typhoid fever, while others are mostly
dangerous to the young, the old, and the sick who can't handle a day or
two of vomiting and diarrhea as well as otherwise healthy people can.

Various Salmonella spp are found in the gut of reptiles, birds and
mammals where they may cause no symptoms.  Note that even typhoid can
be benign in some people -- it's famous for persisting in the gut of
"carriers" who can set off outbreaks over and over again.  Remember the
notorious Typhoid Mary.

Salmonella bacteria usually get onto meat during processing after
slaughter, by contamination from gut contents.  Salmonella may inhabit
the oviduct of chickens and get into eggs before the shell forms.
While intensive farming methods may increase the number of salmonella
infected animals, wild animals can have salmonella in their guts too.
Seafood is sometimes contaminated from sewage discharges, or from
insanitary handling after catch.

Salmonella and other food poisoning bacteria thrive in high protein
foods, and can contaminate cutting boards and utensils when they are
used for raw meat, seafood and eggs, then spread from there to other
foods that are not subsequently cooked.  Many outbreaks of food
poisoning can be traced to these kinds of food handling errors, and
people are trained not to do that sort of thing in restaurant
kitchens.  You should avoid it at home too.

You can eat raw meat without getting sick, just as you can cross the
street without getting hit by a car.  Note that if you look both ways
before you cross, cross at corners, cross with the light, etc, you're
much less likely to get hit.  It also helps to be reasonably fast, and
somewhat lucky.  Not all meat in the supermarket is contaminated, or
from infected animals.  Probably very little is, if it was handled
correctly.  But food poisoning is no fun, and can be life-threatening
for some people, so be aware that you are taking a chance by eating raw
meat.  Sanitary precautions about refrigeration, cleanliness of tools,
working surfaces and hands, etc can reduce your risk of salmonella from
cooked meat, too.  Note that a few percent of slaughtered hogs are
infested with trichinae, a parasite you really don't want encysting
in your muscles, much less your brain, and it's killed by cooking.

Sure.  And they get food poisoning and parasites of various kinds from
it just as people who follow the same practices do.  They don't die in
droves from it, and neither would you.

The Japanese eat a lot of raw seafood and not a lot of meat from land
animals.  I'm sure they use good sanitary practices to reduce the risk
of food poisoning, but they get food poisoning just like everybody else
if they slip up.  Since they eat very little poultry compared to North
Americans they are probably at less risk over all.

Probably not.  Most likely your floor isn't coated with chicken manure
or raw eggs, and it does take a certain minimum amount of bacteria to
cause an illness.

Most likely the fish would be okay if it hadn't been near a sewage
outfall, and you were the only one who handled it, but you can get
tapeworms from fresh water fish, and probably some other parasites as
well.  As for the deer, it would depend on whether it was carrying
suitable bacteria and on how carefully you butchered it. You'd have the
chance to acquire a variety of parasites from eating it raw -- wild
animals are usually very heavily parasitized compared to domestic
ones.

Salmonella is genus of bacteria, not a virus.  There are innumerable
species.  Turtles have some, iguanas have some; they've been around a
long time.  I'm sure people have been getting food poisoning from
bacteria of one kind or another from the first time a hominid ate
carrion, or even before.

Yes, but they consume them immediately rather than letting them sit and
incubate.  Aside from the GI tract, raw flesh from a freshly killed healthy
animal is sterile, so unless it's been contaminated with gut contents or
left to sit and incubate, it's extremely unlikely enough salmonella would
grow to cause illness.  They also don't process them in factory slaughter
houses, raise them on farms, feed them antibiotics, or cut them in butcher
shops with contaminated surfaces and utensils, all of which contribute to
the problem.

But they probably do get parasites and some diseases from their food if it
happens to have been infected.

Beverly's reply was excellent, so I'll leave it at that.