If you are your own company, thus working as a contractor, that's different than hiring an employee to work in an existing company. There are lot of obligations that companies have for each employee in terms of taxes, health insurance, and the like, and in the US they can differ from state to state. If you hire an independent contractor, however, all of those obligations fall to the contractor themself, and the contractor is likely only dealing with one state's laws, so they don't have that complexity.
Consultant isn't a legal definition there is a difference between if they are paying you for services rendered (b2b) or employing you.
Basically unless there is a requirement for reverse VAT charges which isn't applicable to the US there is nothing a company needs to do when hiring a contractor other than pay the invoice, on the other hand there are tons of regulatory and legal requirements that they need to meet when they offer you employment.
