Not too many spiders in the US will bite you with any side effects. The main ones to look out for, however, are the black widow and brown recluse spiders.
Biting Spiders. There is not a lot of them in the United States. Well, there is not a lot that can actually bite you in the United States, there are a lot of species that will bite you. Fortunately most spiders that bite you, are not going to cause too many problems, cause its going to be a sharp sting, unless its a black widow or a recluse. The widow has neurotoxins and the recluse has a skin lesion necrosis type venom. Besides that spider bites aren't much to be afraid of.