Does anyone know a website or individual who has the USAC schedules and other series in a shared calendar?

SprintCarRatings.com has you covered.

You can use this link to view a combined schedule of USAC National Sprints, Midgets, & Silver Crown...
USAC schedules

Or, use this page to create your own combined schedule by selecting which Series, car type, or date range...
Schedule Search

Prebuilt combined schedules...

• Wingless 410
• Midgets
• Wing 410
• World of Outlaws & High Limit
• Central PA (Wing 410)