Do you sump up all Twitter accounts for each brand?
Example: bmw + bmwgroup + bmwusa + BMW_SA + bmwfrance + BMWi_France...
A French twitter user would probably follow the French BMW account, while only the main, US-focus Tesla account is active (cf https://twitter.com/tesla_france)
No, just the one with the most followers. Partly because a single user could follow multiple accounts, but mostly out of laziness