Apparently it's 180 Countries and regions. So every little island is included, even if it's not a separate country. Someone at Google finally learned marketing I guess.
"Regions" is used so that it captures disputed territories such as Taiwan (TWN) and semi-autonomous regions which have country codes but aren't countries e.g Hong Kong (HKG) and Macau (MAC). You will notice that most airlines and international companies now refer to country dropdowns as region dropdowns, primarily to satisfy the Chinese government.