On Tradeshift, accounts can only have one address, which means that accounts can only have one country. You can create an account for each country and note the country code in the company's name, for example Tradeshift UK and Tradeshift USA.

If you want to manage the networks and documents of all of these accounts together, the Branch Management app might be the solution for you. This app allows you to have a master account with several "sub-accounts" as branches.