AFAIK the only setting in s2member that controls currency is the variables cc & default_country_code within the s2Member Pro-Forms shortcodes. As I’m in the UK they’re set to GBP (for Great British Pounds) and GB for Great Britain). I don’t know of any other settings to set.
[s2Member-Pro-Stripe-Form level="1" ccaps="" desc="$1.00 GBP / Monthly (recurring charge, for ongoing access)" cc="GBP" custom="www.domain.com" ta="0" tp="0" tt="D" ra="1.00" rp="1" rt="M" rr="1" coupon="" accept_coupons="0" default_country_code="GB" captcha="0" /]
All supported country country codes can be found here
https://en.wikipedia.org/wiki/List_of_ISO_3166_country_codes