WordPress metaboxes – textfield suggestion automatically populated

I am familiar with Advanced Custom Fields and he has many nice features, but not this one.

Just did some tests with Custom Content Type Manager and looks like it also doesn’t have it.

Case you don’t find a fit one, I think some jQuery may solve your problem using any plugin or hand made meta boxes.

Start with only the main meta box showing (countries). And detect changes in its field value so as to show/hide the second level of meta boxes. This second level will do the same for the third.

Refer to this answer where you have an example of showing/hiding the Featured Image meta box according to changes in the dropdown field Template that belongs to the Page Attributes meta box.

[update]
Another variation I did of the same script, a bit more complex.