When American heads of urban areas legislate in the typical manner (2,5)
I believe the answer is:
as usual
'in the typical manner' is the definition.
(in the typical or usual way)
'when american heads of urban areas legislate' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'american' becomes 'US' (United States).
'heads of' says to take the initial letters.
The initial letters of 'urban areas legislate' is 'ual'.
'as'+'us'+'ual'='AS USUAL'
(Other definitions for as usual that I've seen before include "'In the normal manner (2,5)'" , "Typically" , "Predictably" , "'In the normal way (2,5)'" , "Customarily" .)