The reciprocity page for Sri Lanka is here: travel.state.gov/content/travel/en/us-visas/Visa-Reciprocity-and-Civil-Documents-by-Country/SriLanka.html
- Scan the bio data page of your passport (no translation needed),
- Get the birth certificates from the relevant District Secretariat offices with the signature and the seal of the additional district registrar,
- Then get birth certificates translated by a sworn translator appointed by the Ministry of Justice,
- Get the police clearance online from eservices.police.lk/ClearanceCertificate/home.action. You will get the printed copy by post in 3 weeks.
That's all you need unless you have served in the military or have been sentenced for a crime
. Scan and send them all.