The question here though is not whether people can spell things correctly or correctly identify what state they live in, as whether you can write a computer program to, given what someone claims is their address, reliably break it down into parts to, for instance, extract what state they live in.
If you give someone separate fields for 'city' and 'state' you have some chance of figuring out where they are located if they type 'Washington' into one of those fields. If you ask them just for 'city, state', some people will understand that as 'city or state' and just type 'Washington', and you have no idea what they mean. The example I gave before, LA, is an example of a city which shares its name with a state abbreviation.
An anecdote for you: I was once working with UK callcentre system which had a form for callcentre staff to update customer contact addresses. UK postcodes are combinations of letters and numbers, and certain letters are excluded from certain positions to prevent ambiguous handwritten letterforms causing confusion. I naively implemented strict postcode validation, thinking it would help catch data entry errors. What actually happened was that we ended up, in a significant number of cases, telling people that the postcode that they had been using as part of their address for decades was not, in fact their postcode - it couldn't be because it was an invalid postcode. This made the customers quite cross, and we had to change it.
Do you want your validation message to be the one to break it to some eighty year old guy that Nebraska is actually NE, not NB any more?
If you give someone separate fields for 'city' and 'state' you have some chance of figuring out where they are located if they type 'Washington' into one of those fields. If you ask them just for 'city, state', some people will understand that as 'city or state' and just type 'Washington', and you have no idea what they mean. The example I gave before, LA, is an example of a city which shares its name with a state abbreviation.
An anecdote for you: I was once working with UK callcentre system which had a form for callcentre staff to update customer contact addresses. UK postcodes are combinations of letters and numbers, and certain letters are excluded from certain positions to prevent ambiguous handwritten letterforms causing confusion. I naively implemented strict postcode validation, thinking it would help catch data entry errors. What actually happened was that we ended up, in a significant number of cases, telling people that the postcode that they had been using as part of their address for decades was not, in fact their postcode - it couldn't be because it was an invalid postcode. This made the customers quite cross, and we had to change it.
Do you want your validation message to be the one to break it to some eighty year old guy that Nebraska is actually NE, not NB any more?