Worst Written Alternate Timelines In Media

Most of TL-191, but in particular American Empire and Settling Accounts. Not because they're irredeemable drek, but because they're just so fucking disappointing.

Pretty much everything by Robert Conroy is thinly sketched "I want the US to fight the Nazis alone, the Nazis start off with a few wins to look scary, then GLORIOUS 'MURICA single-handedly saves the day!!!" nationalist masturbation. Even when the enemy is Imperial Germany, Conroy always contrives to make them Nazis before the end of the book.
Ah, but remember one of the unbreakable rules of AH - a post-WWI Germany must always descend into some form of jack-booted Wehrstaat dystopia, whether they win or lose, OTL Versailles or ATL Versailles, no matter what. It's right up there with the inevitability of American Manifest Destiny... :p
December 7th, 1941: A Different Path by David L. Alley.

The POD is Japan saying "Hey, you know how we've been planning to go south to ensure the empire for decades and we just got a really bloody nose dealing with the Soviet Union? Let's attack the Soviet Union!"

This magically results in a TL with the following:
-The Soviet Union completely collapsing.
-Japan invading, holding, and genociding Australia.
-Churchill randomly giving up and surrendering.
-Germany gets the bomb first, nukes New York, and America immediately surrenders.
-America stands as one to oppose the export of the Final Solution to the US
-Albert Speer saves the day by finding out the Holocaust is happening.

*facepalm* LOL.

Sheesh... I thought I'd seen bad.
I admired Harrison's ruddy countenance- which means I liked his bloody cheek!
Harrison went the Hollywood route - don't let historical facts get in the way of a story
Yeah but he gets extra credit for “A Transatlantic Tunnel, Hurrah!l” which is just weapons-grade silly and awesome.
The majority of Turtledove’s stories are cut and pastes of real history with the identities changed to suit his story.

“Wizard of what if”? More like “master of ctrl-c, ctrl-v”
Jeez, what was that one he spewed out that had the American Civil War with blondes instead of blacks and magic carpets instead of railroads that literally functioned exactly like railroads. It had no point whatsoever other than “exactly the civil war, with some cosmetic changes”.
Philip Roth's The Plot Against America springs to mind. He somehow manages to make the fascist takeover of America boring. And far more than general improbability, I'd say the greatest crime an author can commit is creating a boring work. It's 400 excruciating pages of Roth reminiscing about his childhood growing up in 1940s New Jersey, in which nothing memorable happens.