When creating an account, a user can choose to create a Gearset team that has data and metadata stored in the US (or Australia).

However, if your login method is using a Salesforce org, you will see that there are 2 applications that contacts your org for different purposes, this article explains the differences.

The Gearset application which has restricted permissions and is used just to get user details to log you on and authenticate; this will come from the Ireland data center.

The Gearset Deploy application has the permission to query the org and retrieve metadata and data, this request can come from Ireland, US or Australia depending on your user choice.