My organization is a state agency, and we’ve applied for and received EN grant funding twice in the past 5 years. Do we still need to provide an attorney general letter proving my agency is an instrumentality of the state?

If your organization is a state agency, no further information or attachments are needed – you just need an active registration in sam.gov. 

The instrumentality status is only for organizations that act on behalf of a state or Tribe but are not technically a state/Tribal agency/department. An example would be a state or Tribal university or perhaps a local water district that has been delegated state authority. Therefore, you do not need to provide the ‘instrumentality of a state/Tribe’ attachments, as you are a state agency.