I created a module that allows you to select what country you want to have as the default:

https://apps.odoo.com/apps/modules/14.0/jw_website_sale_default_country/

While researching this, I also found that by default Odoo will set the default country to whatever the Company Country is set to in the settings....so you can do either. The reason I thought the module might be better is that you could have your company in one country, but want the default country to be another....I learned a lot trying to get this working, so it was worth while for me anyway.