Русско-англо-русский юридический словарь

An automated teller machine (ATM) or cashpoint (British English) is an electronic telecommunications device that enables customers of financial institutions to perform financial transactions, such as cash withdrawals, deposits, funds transfers, or account information inquiries, at any time and without the need for direct interaction with bank staff. (Wikipedia)

UK proofreader here. I'd use ATM consistently throughout, as international English-speaking audiences are largely familiar with the term despite regional variances. However, I'd also use the full term on the first mention or in the introduction before defaulting to the acronym and provide a mini glossary for the avoidance of doubt at the same time, along the lines of:

Explaining researching that uses data point around automated teller machines (ATMs, also known as cashpoints, cash machines or bank machines) for both American and international audiences. (Ask Meta Filter)