Yes, it’s possible to advertise in multiple countries from one account in BrightBid, it's also possible to have multiple accounts with one country per account.
BrightBid will mirror your account structure in Google Ads, so if you run multiple Google Ads accounts with one account per country or market, that's how the structure will look in BrightBid.
We suggest your setup one Organization in BrightBid, an organization is typically your company, then connect multiple Ads accounts to your Organization.