Public transit systems are only effective in highly-dense, urban settings.
Toll roads are often not within dense urban cities - usually on the outskirts, suburbs, highways, bridges and more. Public transit simply doesn't work in these places because of how large and spread-out the US is.
You’re forgetting how this is all interconnected. Creating the large freeways creates sparse housing that requires freeways. Creating public transport does the reverse.
Before all these massive road developments it’s not like people just sat at home and couldn’t go anywhere.