I'm using Apple Numbers on a Mac with Croatian locale. This means CSV files not only don't have a BOM (byte order mark) which Google Apps requires, but its CSV files are not actually comma-separated, but semicolon-separated. (Croats use decimal comma instead of decimal point, so any CSV files generated by spreadsheets can't use commas. Weird, yep, my dear US reader.)
So… follow Google's instructions in building the CSV file, and then process it with the following commands in Vim.
:set bomb :%s/;/,/g :wq