Notaries Public, unlike JP's and the other similar functionaries such as Commissioners for Affidavits (who are only relevant within their own State or Territory), are recognised and accepted in all foreign countries. As the former Lord Chancellor of England Lord Eldon famoulsly remarked almost two centuries ago… "By the law of nations, notaries have credit everywhere."
What the Lord Chancellor’s statement today means is that a Notary's signature and seal on a document is accepted in most overseas countries without question, subject to the requirement in some instances that the notary’s signature be authenticated or legalised to prevent fraudulent impersonations.
To give an example, a Spanish law court would probably have no idea what a "solicitor", "Justice of the Peace" or "Commissioner for Affidavits" is, but it would certainly recognise the term "Notary Public" as being the same as their "Notario Publico" and more than likely accept on face value the document before it as evidence that it has been properly signed and witnessed.
Australian notaries do not hold "commissions" expiring after a short period of time such being he case in the USA. Generally, once appointed they are authorised to act as a notary for life and may only be "struck off" the Roll of Notaries for proven misconduct. However, in certain States, in particular, New South Wales and Victoria, Notaries cease to be qualified to continue to act once they cease to hold a practising certificate as a legal practitioner. In contrast, American notaries are appointed only for short, consecutive terms.
All Australian States and Territories appoint Justices of the Peace (JP's) or Commissioners for Affidavits and other unqualified persons to take affidavits or statutory declarations and to certify copied documents. However, they can only do so if the relevant affidavit, statutory declaration or copy document is for use within Australia and not in a foreign country; allowing for minor exceptions*** this international function remains the exclusive prerogative of Notaries - the only true "international JP".
Justices of the Peace (JP's) are usually laypersons who have minimal, if any, legal training, although of proven good character. Therefore, a US notary more resembles an Australian JP than an Australian notary.
This is because our USA Notary Public counterpart whilst also administering oaths, taking acknowledgments, and performing other wide ranging and useful functions, is not a qualified lawyer with legal training and consequently is not permitted to offer or give legal advice or prepare legal documents.
***The circumstances in which Australian JP’s (or other functionaries) may witness international documents are relatively few and far between. Documents intended to operate in a small number of Commonwealth countries including former or current British Territories, are probably the only exceptions. JP’s’ signatures to international documents cannot be legalised by the issue of an Apostille Certificate (Western Australia excepted).