There are two ways to change the default country in the SEO toolbar:
Keyword metrics shown for the searched keyword.
The country which the google search is conducted in. (Can be changed using Local search simulator)
Both of these countries can be changed in your toolbar. To do so, open the SEO Toolbar window by clicking on the extension's icon and click on the Search tools tab.
Changing the default country for keyword metrics
To change the default country used to show Keyword metrics like search volume, global volume, CPC and more, select the country of choice in the dropdown field in the Search settings section. Settings are saved and applied automatically once a country is selected.
Changing the default country for the Local search simulator
Configure the desired location, along with Google's domain, language, and device, in the Local search simulator section.
Settings are saved and applied automatically once the dropdown fields are applied, but existing search results pages won't be changed. To search google with the new settings, click on the orange "Search" button.
You can confirm the country has changed based on the country indicated respectively:
Related: