Why can't I access Google and other sites when tethering my phone?
Resolution

EasyTether Light (No Root) is the best tethering software I've been able to find on the Play store; however, it blocks UDP ports and secure protocols.  Updating to EasyTether Full (cost: 9.99 USD) resolved the issues on all of the above-listed sites and services.  It was very bothersome to go through all this and e-mail the developer, only to get a kind of boggled response from him.  Their FAQ does not mention this, and the message in the app was covered up by the "warning, do not scratch the camera" message I had written on my screen guard, up until yesterday; so, I simply didn't notice.  I hope the developer will upgrade the app to include some kind of pop-up message indicating that this is the cause of the issue, or at least add the issue to the FAQ.

Thanks for all the comments and wonderful help!