Originally Posted by JJeffrey

You're thinking about it the wrong way. The oneworld rules say any First or Business class flight (all destinations all oneworld carriers) comes with lounge access. AA then has it's own exception within those rules that say business class flights wholly within N. America do not get lounge access, except for MEX and the premium transcons of JFK-LAX/SFO and MIA-LAX.

Basically any oneworld F or J flight comes with lounge access by default unless it specifically called out as an exception, and MIA-LAX isn't included in the N. America exception, so good to go.