I have rented in the USA before but no longer have an IDP (International Driving Permit). They seem rather unrecognised. I wasn't required to have one when I rented last year.
What do you think my chances of needing one are when I visit Washington DC next week? I would hate to be stuck without a car! Will photocard and counterpart suffice?
Green Flag (who issue IDPs) show the USA under 'recommended' rather than 'required' in their list of countries where you might need an IDP.
I've never been to the US, but the fact that the IDP is only 'recommended' (together with the information that you didn't require an IDP last year) suggests to me that you should be able to find a company which will hire you a car (but some companies might still refuse to do so).