Ok, picture this. The year is 2006, about halfway through the Bush Jr Administration. The US is embroiled in conflicts in the Middle East, and elsewhere, and for these conflicts, they rely heavily on their navy. Sure, there's various aircraft carriers, both nuclear, and conventional powered ones, as well as Arleigh-Burke and Spruance destroyers, AEGIS cruisers, Oliver Hazard Perry frigates, and various other ships like them, but alongside them are ships of old, that never really left service. All 4 of the Iowa-Class Battleships are still in service, as are all 4 South Dakota-Class Battleships, and both North Carolina-Class Battleships as well. These 10 battleships act as command vessels for the various fleets they're attached to, and they're all equipped with the latest radars, fire control radars, and missiles, alongside their massive 16in guns, 5in guns, Phalax CWIS, and various other weapons, such as the M242 Bushmaster chaingun, and Browning M2's. But they're not alone. Other battleships from the past are also around, but they almost strictly have their weapons from WW2, despite modernization's to keep them up to date, but their role is mainly shore bombardment, and fleet escort duties, as well as projecting American sea power abroad

Also joining these battleships are the battlecruisers USS Alaska CB-1, USS Guam CB-2, and USS Hawaii CB-3, all upgraded to modern standards, as well as the heavy-cruiser USS Witchita, the Baltimore-Class, Oregon-City Class and Des Moines-Class heavy-cruisers, and a plethora of late WW2 light cruisers as well, namely of the Brooklyn, Atlanta, Cleveland, and Fargo-Classes as well. And like their larger heavy cruiser and above brethren, these light cruisers were also upgraded to modern standards, and while some were kept in all-gun configurations, some gave up most of their guns for missiles, though they lacked the severe stability issues of these types of cruisers in our timeline. How is any of this even possible? Well, I'll tell you

In the aftermath of WW2, and the rise of the Soviet Union, Communist China, and other threats, it was realized that the US needed to maintain a strong navy, so it was decided to keep many of the ships that came from WW2, and slightly beyond, but almost everything from early WW2, and before were decommissioned and scrapped, with a few vessels of historical significance being saved, such as the USS Oregon BB-3, the USS Texas BB-35, and the USS Enterprise CV-6. Over the years, various other vessels, chiefly aircraft carrier classes, and various destroyer classes came and went, with the older heavy cruiser and light cruiser classes also being retired, with a few here and there being saved, but most being scrapped. And as time went on, new upgrades were being given to the ships that were still in service, including better radar and fire control radars, various processing systems, and even automating their gun systems so as to cut down on crew requirements. Eventually, almost all ships had some variant of the Mk 16 Rapid-Fire Auto-Loading 8in guns found on the Des Moines-Class Cruisers, just in 5in, 6in, 12in (Alaska-Class only, and these were later upgraded to 14in), and 16in. Shells were also improved, both increasing their range, and making the shell and its charge a single unit, making them able to be rapid-fired with great accuracy. And with this vast navy, the US would deliver devastating losses to North Korea and China in the Korean War resulting in a US-South Korean victory, and the reunification of Korea in 1955, massively cut US Service casualties in Vietnam, and the presence of so many warships constantly bombarding North Vietnam, supply lines for the Viet-Cong in South Vietnam, and bases used to supply them in Laos and Cambodia, The Vietnam War ended in a US-South Vietnam victory, and reunification of Vietnam in 1970, keeping the Soviet Navy in check in the 1980's, dealing with various threats around the world in the 1990's, and of course, unleashing hell on Sadam's forces in the Gulf War, and back for Round 2 in the Iraq War. No other navy in the world was able to stand up to the might of the US Navy, and its massive fleet of aircraft carriers, battleships, heavy cruisers, light cruisers, destroyers, frigates, and more.

What do you all think of this Alternate-Timeline where the US held onto these various classes of ships for so long? What do you think the world would look like today if world history played out like this?

There were significant numbers of US big-gun ships left over from WWII fighting in Korea. In fact, there weren't very many in existence that didn't participate. I don't see a handful more of them making a huge difference.

USS New Jersey was activated for Vietnam and spent five months on the gun line, making an impact, but apparently not enough of one to show cause to reactivate any other ships or even send New Jersey back for a second tour.

I'm not sure what you're getting at for 2006. There has been no conflict in the last thirty years where naval gunfire support would have made a difference.

I do, however, agree that a large navy is important, even if it's not battleships.