CourtListener (from the non-profit Free Law Project) provides bulk access to its case law collection.[1][2] I expect they are ingesting the GPO uscourts collection so it should have near complete (99%) coverage.[3][4]

[1] https://www.courtlistener.com/help/api/

[2] https://www.courtlistener.com/help/coverage/

[3] https://www.govinfo.gov/help/uscourts

[4] https://www.courtlistener.com/help/coverage/opinions/