Store Locator Plugin Guide
Why the Google Map Zoom In on the Page Load?
As you have set the zoom value to a small number to show a global view in the store locator once the page is loaded and that is not happening for you, there may be a couple of reasons that features may override to change the zoom value on the page load.
You have set a value of 4 to the zoom of the map so the entire world should appear but as it is not happening for you, please validate the step below.
Make sure that the Default Location Marker is disabled, the purpose of this feature is to tell the widget to consider the default location as the center point, and if the distance controls are enabled such as they have 20 miles at the moment, the view will zoom to 20 miles to the default location and it will no longer be zoom value 4, rather it will be around 18 to 20 instead.
In case the above setting doesn't work for you, please try to override it via the shortcode.