Partial answer
According to https://en.wikipedia.org/wiki/Date_format_by_country,
the following locales use YMD date format:
Afghanistan, Albania, Bangladesh, Cambodia, Canada, China, People's Republic of, Denmark, Germany, Hong Kong, Hungary, Iran, Japan, Kenya, Korea, Latvia, Lithuania, Macau, Mongolia, Myanmar, Namibia, Nepal, Norway, Singapore, Slovenia, South Africa, Sri Lanka, Sweden, Taiwan,Republic of China, United Kingdom, United States of America
Notes
I didn't find a simple table that combines the date format and currency symbol but find the following that could help
Other interesting findings
Spefications / open source projects
Google participates in the below projects, so is very likely that Google Sheets use them
The Unicode CLDR provides key building blocks for software to support
the world's languages, with the largest and most extensive standard
repository of locale data available. This data is used by a wide
spectrum of companies for their software internationalization and
localization, adapting software to the conventions of different
languages for such common software tasks
ICU is a mature, widely used set of C/C++ and Java libraries providing
Unicode and Globalization support for software applications. ICU is
widely portable and gives applications the same results on all
platforms and between C/C++ and Java software.
Tools
This demo illustrates the International Components for Unicode
localization data. The data covers two hundred five different
languages, further divided into four hundred eighty-eight regions and
variants. For each language, data such as days of the week, months,
and their abbreviations are defined.