N5B Form for foreign landlords

Possession - Section 8 and Section 21

We have issued a Section 21 notice to our landlords tenants, which expired 2 days ago. They have asked us to proceed with posession, so we are in the process of filling out the N5B Notice. My landlord is a foreign resident living in the USA, but under claimant address, it just says 'county' rather than 'country'. What address should I input here? I will be sending the form to my landlord for them to wet sign and post back so want to get this right. So far I have been given differing advice (one saying to use the agent address which I don't believe is correct). The landlord does not have a solicitor so we don't have a legal representative address. Thanks