You will need to identigy which YARN Daemon enforces that parameter and if needed will need to restart that Daemon accordingly.
Ex:
EMR Master has YARN ResourceManager
EMR Core has YARN Nodemanager
If you need to change a parameter that corresponds to YARN ResourceManager(like yarn.resourcemanager.*), then you might need to edit yarn-site on just master and restart just the ResourceManager daemon.
If you want to change a parameter like yarn.nodemanager.* , then you will need to change yarn-site on all core nodes and might need to restart NodeManager daemon on all core nodes.
Now, when it comes to how to change this setting on all core's at once, there are lot of tools out there to do it(Like Ansible, PDSH , AWS SSM etc. ). EMR does not have any API that supports changing config's on fly. If you are trying to provision a cluster with desired configuration , use EMR Configurations API. https://docs.aws.amazon.com/emr/latest/ReleaseGuide/emr-configure-apps.html