Is there a Google app for PC that allows offline access to Google Docs, Sheets, and Slides?

Yes, the Google Docs, Sheets, and Slides apps (integrated with Chrome) allow for offline access. You need to enable offline access in the Google Docs settings. This functionality syncs your documents to your computer, allowing you to work on them even without an internet connection. Changes are synced back to the cloud when an internet connection is restored. The Google Drive app also contributes to offline access for files stored in Google Drive.