

The country overnight decided…
Your country was changing…
you do realise you’re on the World Wide Web, right? Please stop acting like there’s only one country in the world, and that’s the omnipotent, wonderful USA. That’s what the message you’re replying to refers to: 9/11 was important for the USA, but the world is much bigger.
I would understand that “swarm” here is used as a noun, destroy is the verb. The verb uses the third-person singular form (destroys) therefore the subject can’t be “1 million antelopes” (plural), but should be singular, like “one swarm of antelopes”.