Is there a way to add super admins to ALL sites without having to add them to each site individually? My group of super admins needs access to all sites.
Super admins do have access to all sites, but they don't show up in "My Sites" by default, which I imagine is where you're looking. They'll want to go to the network admin (/wp-admin/network/, then go to all sites from there, then find the site they want to edit and click "Dashboard" (which appears on hover).
I like to think of "My Sites" almost as favorites, and only add myself to a site when I'll be accessing it frequently, as it reduces the list I have to pick through.
Does that make sense and clear up your question?
Or For adding your sites on "My Sites" if you've missed them, then you can add them by go to Network Admin > Dashboard > All Sites > Edit Your Desired Site > Users (Tab) > Add Existing User > Add your desired existing username and role it as "Admin"