Learn English – Would the phrase “No worries!” be understood outside Australia

"No worries" is fine in speech, and you would want, perhaps, to follow it with something hopeful, such as,

"No worries; you still have three more tests you can make it up on." - or -

"No worries; there are plenty of fish in the sea."

"Leave all worries" is formal and a bit poetic. It is used in songs; it is common to read it in the phrase "Leave all worries behind you," or the saying, "Leave all your worries at the door." It isn't used much in conversational (AmE) English, except by religious people, who often advise others to "leave all their worries at the foot of the cross."

It generally means "it is your responsibility." By responsibility it means that the blame or the victory would belong to you - sometimes it is said when someone is taking a risk or doing something that could go badly. The person saying it means "it is your choice, but don't blame me if it fails." Particularly in superhero movies where people are doing dangerous things all the time.