Do all US providers for wireless services (who support SMS) give users
an email address at which the user can receive text messages?

Are you looking for this service to be available to you, for your
carrier or generally available?
Generally, it is possible to use third party forwarding, such as
http://www.mailsurf.com to get your email forwarded to your phone and
vice versa. This is how I do it.

Another option available through many carriers is the carrier provided
address. This will usually be something like
yournumber@serviceprovider.com. There is sometimes an additional cost
for this service. A problem with it is that spam may come through to
your phone if you choose to have incoming mail forwarded. Filters can
avoid this problem to a certain extent by choosing certain subjects or
senders for mail to be forwarded from.

If you give me the name of your carrier, I would be happy to find if
the service is available and provide instructions to set it up.