The 'bracket' refers to a type of rhyming slang from 'hinge & bracket' meaning hinge - whinge, and the phrase is reversed to encode it, so bracket right means 'right whingers' - meaning Americans.
'Maintain angels 15' is a reference to the course steered, angels being track with applied drift and 15 being 150 mils (about 050 degrees).
See, easy when you know how!