And once again, 2009 Trek established an alternate TIMELINE because of old Spock being sent back. Not an alternate UNIVERSE!
It’s clearly stated by Spock in the movie.
Old Spock was clearly suffering from Vulcan dementia. A supernova threatened to destroy the entire galaxy? Its blastwave propagated faster than light? And anyway, things were already different before Nero's ship blipped in. The
Kelvin and its technology and uniforms and
everything were all wrong for pre-TOS.
As for "Future's End", we never saw a newspaper and only caught a glimpse of the news Neelix was monitoring. Even in a conflict like WWII, people in America -- where the fighting was not directly taking place -- were trying to live their lives and keep things as normal as possible. And that conflict potentially involved a larger portion of geography than the fight to shut down Khan.
I still like the notion I've seen that 23rd-century historians look back the way we do at things like the Thirty Years War or the Punic Wars and recognize WWI, WWII, the Cold War and proxy wars the US and USSR fought during it, and WWIII as one long interlinked conflict -- which they are -- collectively called the Eugenics Wars. In the original timeline, where things diverged from ours even further back (early 19th century at the absolute latest), things stayed hotter through the 1960s and we got more of what NASA and the Air Force were promising during Mercury and Gemini -- widespread atomic power, orbital weapons platforms, manned moonbasees, etc. -- and, in that shifted sequence of things, Khan and his followers came to power and, by 1995 when he was defeated, came to control "a quarter of the globe". Ancillary fiction had determined that was a lot of Central, South, and East Asia.
There was never any indication America was the site of any of the actual fighting until WWIII, so Los Angeles of the 1990s would have likely been as we saw it. It
is all gone by the 23rd century, though. Dunno how much Braga knew or cared -- if he ever showed any continuity with older lore, it was likely accidental -- but Gene held that much of the SoCal coast was unrecognizable from how we know it, due to a massive earthquake. In his novelization of TMP, he has Kirk transfer from the orbital shuttle to the local at the "Los Angeles Island" transit hub.
And, lastly,
they need to stop with the time-travel, already! All of it. They do it badly. They always have. It's made a swiss cheese of the scaffolding of the setting, no one can rely on anything, writers can and do change anything they want from what was established, using time travel to explain or justify sloppiness, laziness, or hubris -- or all three. The
only exceptions I'll allow are Q and the Guardian of Forever, because they follow their
own rules.