Setting up shipping methods by country
If you offer both domestic and international returns, you might want to create some rules to make sure that your customers are only seeing shipping methods that are relevant to them. For example, if you're based in the US but accept returns worldwide, and have USPS, DHL, and mail-in as your shipping options, you might not want your international customers to see USPS as they wouldn't be able to use it.
Since all the shipping methods will be connected (e.g. USPS and DHL), you'll need to restrict the options that certain customers have.
For international returns, you'd set up a rule excluding US customers, and select only Mail and DHL Express so that customers based outside of the US will only see these two options.
If you don't want to offer DHL Express to domestic returns due to cost or any other reason, you'd set up a rule including the US customers and select USPS and Mail.
Please note that you need to include the full name for countries, so for the US you'd need to add "United States", and for the UK it would be "United Kingdom". You can also use multiple countries in these fields separated by a comma (e.g. United States, Canada).