Why do you need two keys? If the same VM needs to access both buckets can’t you simply grant the VMs service account permissions to both? Or perhaps I need a bit more understanding of your scenario.
Ok in details I want to securely access the Bucket one created in US with separate project and another one created in UK another project
now the instance I created in US with US project now how do I access the two different project bucket to be access
if it’s a gcp VM, you shouldn’t need to configure any service account; you should have implicit access with the identity of the service account attached to the machine itself (either the project default compute one, or a different one, if configured