In general answer is "yes", you can setup two keycloak instances in different locations, and link them with each other via cluster (under the hood it would be infinispan cache replication). But it depends on details of your infrastructure.
Main goal of Keycloak cluster is to perform sessions cache replication between nodes. So in simplest case you can setup two nodes that looks to same DB instance, and when first node goes down second would handle whole job, but if DB also goes down second node would be useless. In such case each site should have both separate Keycloak node and DB replica (how to achieve DB replication is out of scope of this topic). Third option is to use multitenancy feature of keycloak application adapter, in that case you secure application by two separate Keycloak instances, that know nothing about each other.
Try to start from this documentation article: https://www.keycloak.org/docs/latest/server_installation/index.html#crossdc-mode