Google announced that it will be retiring the API for Google Earth on December 12, 2015, or a year from today. The decision to retire the Google Earth API comes after both Chrome and Firefox had dropped support for the NPAPI plugin framework, and Google also cites decreasing cross-platform support.
In a blog post, Google announced:
However, the Earth API is built on a technology called the NPAPI plugin framework, and recently, for security reasons, both Chrome and Firefox have announced they're removing support for this framework. These security reasons, combined with dwindling cross-platform support (particularly on mobile devices), had made building applications that leverage the Earth API untenable for developers.
You can read more about Google's decision in the source link below.