
Is notarisation the
same as legalisation?

No.
A notarization, or notary signature and notary stamp, placed on a document can only be done by a licensed notary public in the United States.
A legalisation (legalization) is a certificate or attestation placed on a document and can only be issued by a foreign U.S embassy, consulate, or consular office once a document is physically presented to them by mail or walk-in service.