It's not a matter of geography. It's a matter of language. In English, a period acts as the radix point and a comma acts as a separator. It's a common error for people who learned English as a second language to use the convention of their native language when writing in English.
No, it's a matter of geography (or should I say locale). Raised in South Africa, we English speakers were taught to write "ten thousand and forty one-hundredths" as
10.000,40
which is exactly the opposite of the US based
10,000.40
So it's locale rather than language that determines this.
