When Site B responds with a JSON file of data, the Intersite Communication action in Site A receives this, and stores it in a Large Text field:

In Site A:

In the Intersite Communication table we already have this configured in the Intersite Communication action:

where in the Response section, we map the JSON field.

Once stored in the Large Text field, we can use a Data Import action to pass this to a Data Import component which can process this:

Data Import component: