How do I disable iMessage on every computer I installed with my email address?
Though I don't believe there's any way to do a broad-sweep method, you can disable it on a case-by-case basis on OS X and iOS.

OS X

Open the Messages app, then in the menu bar hit Messages -> Preferences. Click on the Accounts button, then your iMessage account in the sidebar. Uncheck the box labeled "Enable this account."



iOS

Go to Settings -> Messages and turn iMessage off.