Many people do not realize when you cross state borders for commercial purposes, you need to register in the other state. Each state has a right and duty to protect its citizens.
If an NV business does business in CA without registering in CA, and the CA consumer is dissatisfied, they have no recourse except in Federal court unless the business is registered in CA.
The transaction takes place in CA, so NV courts have no standing. If the business has no CA registration, the CA courts have no reach. Thus a citizen from one state suing an entity from another state goes to Federal court.
To register in a state, you need a registered agent; someone with a physical address in that state that can accept process service for lawsuits. There are many companies out there that provide this service.
Whether you are subject to also registering with the different revenue offices within each state, and whether you will be subject to their sales tax is dependent on other factors. Generally if you regularly sell something in a state, even if you have no physical presence in that state, you are subject to their sales tax laws.
Certain industries have their quirks. For example CPAs have an exception as long as they do not travel to the other state. The reason for this is the state board of accountancy will stand up for the disgruntled client from the other state, and the transaction occurs at the CPA's desk unless they travelled to the client even if only to say hello.
