Yes it’s true the US hasn’t introduced a new ICBM since the PeaceKeeper. However in the late 1980s early 1990s there was the Midgetman missile system or SICBM which was supposed to be TEL launched.
Peacekeeper was also supposed to be TEL launched off the back of a Train but they plugged them into existing Silos as an interm solution because no one wants to be sitting behind an ICBM in traffic.
I still remember to this day the endless discussions about the best way to base MX (Peacekeeper).
There were no news programs and magazines at the time, at that time, TVs, newspapers and magazines were focused on information. I vaguely remember a proposal to base 100 MX in a network of underground tunnels with more than 4000 launch points. The Soviets would have no way of knowing where the missiles were and would have to attack 4000 points, which was unfeasible.
Another proposal was to install the 100 MX all together in reinforced underground silos close to each other. They would be far enough apart to require a warhead to neutralize each missile in their silo, but close enough so that they could not be attacked at the same time since the detonation of a warhead close to another releases such a quantity of neutrons that it renders the missile useless. second warhead.
There were other proposals, such as installing the MX in silos on the edges of mountains so that the enemy warhead could not fall close to the silo and the mountain would deflect the shock wave.
In the end, they only made 50 MX and installed them in the old reinforced Titan missile silos, which together with around 900 Minutemans made up the US ICBM force, which today has been reduced to 400 Minuteman IIIs, each with one warhead.
The US remained with 1054 ICBMs for a long time. There were 500 Minuteman IIs with a 1.2 Mt warhead, 500 Minuteman IIIs with 3 MIRVs(170 Kt), and 54 Titans with a 9 Mt warhead. The Americans decided to retire the Minuteman IIs and Titans and instead deploy 50 Peacekeepers ( MX), which would have 500 to 600 warheads.
After START I, there was a reduction in nuclear weapons and the Americans dismantled the new MX, leaving only the older Minuteman IIIs. And yet they were forced to remove the MIRV warheads and installed a single warhead (SRV- Single reentry vehicle).
They could have kept the 50 MX and kept 500 warheads, but they preferred to keep more missiles (delivery means) with just one warhead. Even though in theory it would be more expensive to maintain 450 ICBMs (they retired 50 and now, it seems like 50 more, due to a new reduction imposed by START), the US would prefer it to having fewer missiles with more warheads.
Just out of curiosity, there is information from a few years ago that some Minuteman IIIs were once again armed with 3 MIRVs, which is somewhat worrying because it shows an increase in tension and mistrust between the US and Russia.