The Spaniards brought domesticated swine, pigs, to the Americas starting in the late 1400s to early 1500s. The Spaniards deliberately let loose pigs (also goats) on islands so they could, on later voyages, hunt "fresh meat." Also they brought pigs as they established farms over here. Some got lose and became "feral pigs," living in the wild (on some islands, they created eco-nightmares).
Then about 100 yrs ago some rich guys imported Russian "boars" to North American - non-domesticated swine - for hunting. They mixed with feral swine - so the wild boar we see in America is usually a hybrid (not always - there are pure feral hogs and pure Siberian boars).
The eco "damage" boars do is... in some cases overstated. It kind of depends. They're hunted because: some people enjoy hunting, boars taste pretty good, the meat is often free (save the cost of a bullet), and/or someone wants a boar's head mounted and hung on their wall. Crop damage is a far greater problem - farmers can offset this by charging city hunters big bucks to come hunt boars on their land.
Ranchers who don't care much about swine damage (cattle eat grass, swine don't compete much for that) sometimes create "barrow hogs" - I think that's what they are called. They live-trap young boars and castrate the males, then release them. Their meat is much more tender that way, and because they don't sharpen their tusks (lack of testosterone, lack of aggression) - their tusks get long and weird looking. Then they offer city hunters the chance to hunt something that is tender and tastes good - for bick bucks - er, money, not male deer (but the "buck" derives from a male deer, or buck - but that's another story).
Hunting boars - in barley and corn country, this meat actually tastes good. Desert boars in California can taste strange, as they eat weird desert plants and have to scavenge more. Boars w/ access to beaches are the worst - they eat almost anything that washes ashore, including dead fish - yuck. Boars really do eat anything (except eggs and cooked eggs, what's up w/ that - worried about cholesterol?).
In ancient Macedonia, a rite of passage into manhood included facing and killing a wild boar w/ a spear - actually very dangerous. Boar spears have a "T" or cross bar on them about one to two feet down from the point - why? To stop an enraged boar from working itself up the spear (further impaling itself) to gouge the hunter! Tough beasts!!!! A boar can get so mad it will just shove itself up that spear, ignoring the pain, to try to kill the guy who stuck him! OINK!!!!!!
I know someone who, in S. Africa, was attempting to live-trap warthogs (very similar to boars) to sell to wildlife parks - and one turned on a friend who was helping. The warthog stuck him w/ a tusk just above his crotch and jerked up, hard - and my friend said it was as if he'd been "unzipped" up to his breastbone. It was horrible - a horrible way to die - and a horrible thing to see. Anyway, these creatures are deadly.
Most boar hunters I know always carry a back-up gun, often a .44 Magnum revolver - just in case. Boars will turn on the hunter and charge!
Phear the Boar! Got Oink?