colloquial language - How does this meaning of 笑えないかな work?

In this Bump of Chicken song, the line 笑えないかな is used a number of times.

For example:

全て受け止めて笑えないかな

If only I could just accept everything and smile.

誰かに優しく出来ないかな　全て受け止めて笑えないかな

If only I could be kind to someone. If only I could accept everything and laugh.

笑えないかな

If only I could laugh.

The translations are a combination of those provided online, my native speaker friends and mine. If I translate 笑えない literally I come up with "I can't laugh." With 笑えないかな, I get "Can't I laugh?" So how does "Can't I laugh?" become "If only I could laugh." I see the correlation in meaning but I am not 100% there in understanding it. I guess verbない + かな has this nuance of "If only.."

The more literal way of saying this phrase would be ”笑えたらいいのになぁ” "If only I could laugh." But how does this colloquial version work?