Yes you're absolutely right, when not specified otherwise the application will compute a map "default location" from the outline.
It does work fine for most maps but not for those with particular shapes (which is the case for the USA when you include Alaska and Hawaii).
Instead of the preview location, you can use this dedicated field:
Code: Select all
Having a separate tag allows you to have a nice looking location for the preview and a useful location for the default location.
PS: I've update the online of the USA TopOSM map to only include continental US (as this map does only cover it), the default location computed from the outline is now pointing to a correct location. Thanks for the report.