I propose URSSI should host both working groups and interest groups.
Working groups would be proposed to an URSSI board with a charter/charge, and a timeline by which they would accomplish their work.
Interest groups would be proposed to an URSSI board with a charter, but would be aimed at discussion, not accomplishing work, with no fixed end date, but perhaps a brief annual check to ensure it was still active.
In both cases, the group could already exist and could be co-branded as URSSI, or could be created jointly with one or more other organizations.
These groups could focus on topics of interest to the US community, or could be global.
URSSI would supply a web environment under which the groups could post material, potentially a communication channel for meetings if needed (e.g., zoom), and perhaps a wiki or discourse for discussions.