First of all, please recognize that the Northwest Coast Culture Area encompasses an enormous area, from California to Alaska, and there were hundreds of tribes and tribelets resident there. There is plenty of room for a variety of political organizations to develop. It is interesting, then, that for the vast majority of the area, there was little or no political organization. The literature suggests that in most cases, the largest, and only political entity was the household. According to Ames (2003):

The corporate household ranging in size from 15 to well over 100 individuals, was the coast's fundamental social, political and economic unit. Households owned and controlled estates of corporeal and non-corporeal property that included rights to exploit resources in particular patches [think gathering areas]. They also had outright ownership of some patches as well as privileges such as titles, songs and dances.... Large post and beam houses were among the household's major possessions.

Rich families had more influence than poorer ones by virtue of their prestige, ownership of dance regalia and other properties, and the ability to "buy" settlements and thus end disputes. And disputes were common. Baumhoff (1978) describes areas of far Northwest California as being so rich in resources that the residents had little more to do than "bicker and litigate disputes"

Northwest Coast society was clearly stratified. There was a "chiefly elite" (mostly heads of households), free individuals and slaves.

So what was the situation in the 1500's? Well, we really don't know because the historical record doesn't start for another 300 years or so. Archaeological research suggests that social stratification probably began about 3,000 years ago and that the beginning of cultural complexity may be as early as 4,500 years ago. However, there is no evidence of centralized (in the political sense) nations until well after contact.

With regard to your question about long distance travel and trade, it begins very early. There is evidence of obsidian trade at least 9,000 years ago. And there is evidence of coastal trade to eastern Washington in the form of Olivella shells at the Marmes Rockshelter dating to at least 7,000 years ago, and maybe 9,700 years ago. Trade networks were evident throughout the Northwest. The most common transport was by canoe but there is ample evidence of overland trade routes used on foot and later on horseback. I suggest you see this post by u/The_Alaskan. It has quite a bit of information on trade along the west coast.

Ames, Kenneth 2003 Evolutionary Anthropology Volume 12, Issue 1. The Northwest Coast.

Baumhoff, Martin 1978 Environment. in Handbook of North American Indians, Vol.8, California. Smithsonian.

R.G. Matson and G. Coupland 1995 The Prehistory of the Northwest Coast. Academic Press, London

Lee Lyman 1991 Prehistory of the Oregon Coast, Academic Press

Were there states like the Iroquois Confederation?

Speaking for Coast Salish, Wakashan, Chemakum, Sahaptin, and Chinookan tribes...No.

Villages were mostly autonomous from one another (demonstrated when treaties were being signed as Chieftains often believed they were solely representing their own village and not the entire tribe) while marriage ties would align certain tribes to encourage trade and prevent war.

Is there evidence of trade with other parts of North America or Mesoamerica?

That heavily depends on where you're asking about (besides Mesoamerica).

In WA, the Coast Salish tribes of the Puget Sound traded heavily with the Sahaptin tribes across the Cascades, with Whalebone implements such as war clubs being found in archaeological sites to the east of the Cascades.

Were there road networks for trade and travel in the region?

Not really. Coastal tribes would mostly use canoes for traveling, while mountain/hill paths would be rather simple.