Many former European colonies are mostly bilingual, e.g. Africa is highly multilingual out of necessity. Much of Europe itself is also mostly bilingual. If you want to communicate outside your own little region and your native language isn't a lingua franca, you need to be bilingual in this world.
The main holdouts when it comes to bilingualism are former imperial powers who managed to both kill domestic language diversity (e.g. France, UK, Russia) while also spreading their national language as a lingua Franca. Another group of holdouts are settler colonies such as the US, which didn't have a dominant native population after the arrival of Europeans.
But even if e.g. Russia itself isn't super bilingual, the rest of the former Soviet Union certainly is, since that is just the reality if you live in a small and/or formerly colonised country.