A nosotros ___________ interesa aprender más español.
same logic as the a ti te encantan las manzanas
a nosotros is to us
so we need the reflexive us nos
A nostoros nos interesa aprender mas espanol.
We are interested in learning more Spanish.
But English doesn’t like the passive voice.
So it is better to say
We want to learn more Spanish.
That is one of many reasons why English speakers have so much trouble with translating the reflexive pronouns