It's 'useless' trying to change her mind. = It's 'useless' to try to change her mind.
Drugs are 'useless' in treating the condition.
I made a 'useless' attempt at fixing the leak.
(..) the whole blessed day. l see, not there. Then please, can you tell me-- --. Thank you. Good-bye. Mama, it's useless to call. He's a busy man, could be anywhere. He won't remember anymore. Come on, let it go. He hasn't been here in years. (..)1988 Cinema Paradiso