ACH is a US dollar bank transfer system between US registered and regulated banks.
"Overseas ACH" isn't a thing; anything which looks like it is fronted by a US institution
"Overseas ACH" isn't a thing; anything which looks like it is fronted by a US institution
>There are various ACH systems around the world. The World Bank identified 87 systems in their 2010 Survey
Seems to me like there are many different ACH systems, but perhaps the one referred to colloquially as ACH is specifically FedACH, the American system.
There are many national and international equivalents, but the linked Wikipedia page gets many of the examples pretty wrong, listing e.g. card acquirers/processors and central banks as examples for other such networks.
Direct equivalents would e.g. be SEPA Credit Transfer (but not SEPA Instant) and SEPA Direct Debit in the Eurozone or FPS (credit push only) in the UK.
Giro might be the other, possibly broader term for something similar:
https://www.nacha.org/content/international-ach-transactions...
It still Nacha which is a US institution as you mention. However, I don't see how that protects in the case of a fraudulent overseas transaction. What recourse do you have if an overseas bad actor tricks you into sending money to his overseas account via international ACH?
1) settle the transaction in the next few days (3 usually).
2) ask for additional information on the next few days.
3) deny (return) the transaction if it looks too suspicious according to the bank.
[1] https://www.nacha.org/system/files/2019-07/IAT-Specific-Data...