Auto zoom enable/disable is back on the nuvi 37xx series under v3.60

Hard resetting my US 3790 running firmware v3.60 and changing the locale to Australia (done at bootup immediately after the hard reset/clear all user data) *enables the auto zoom on/off toggle feature* that some users are mentioning in other forums. Go figure. The auto zoom enable/disable is under Tools>Settings>Navigation>Automobile>(arrow-down)Auto Zoom. The unit seems to work fine (so far) but of course, you'll need to change the units setting to Miles rather than Kilometers (Tools>Settings>System>Units). Also change the time format to 12-Hour rather than 24-hour (Tools>Settings>System>Time Format). Also change the Language settings to reflect that you're in the US (Tools>Settings>Language).

The Auto Zoom enable/disable is located under Tools>Settings>Navigation>Automobile>(arrow down)Auto Zoom

Traffic is unaffected by the locale change.

One visual difference is that the speed limit icon at the lower-right of the moving map is changed from the US's black numerals on a white rectangle to the EU style red-bordered white circle.

A Hard reset (or clear all user data) can be done as follows:
From the moving map screen, press the Speed field in the lower-right corner. Now press and hold the compass heading just above the speed in the round speedo dial for ~7 seconds. Select "Clear all user data" and follow the prompts. Upon the next bootup, you can select the Australian locale.