нами is the instrumental case of мы https://en.m.wiktionary.org/wiki/%D0%BC%D1%8B#Russian
If you enter (in English) "The bridge is in front of us." and "the bridge in front of us." into Yandex, the Russian is identical to this question:
мост перед нами.
So in a way, you're right. If they had left the period off the end of the Russian answer it could go either way.
But the presence of the period/full stop tells me that this is intended to be a sentence and "The bridge in front of us" is not a complete sentence.