Considering how Prime was obliterated by a tactical missile bombardment executed by Bradley-Hercules, it's also very likely that Liberty Prime would've been destroyed in the war.

TL;DR Liberty Prime would've sped up the liberation of Anchorage which would've led to an earlier invasion, but if used to invade China, he would most likely have perished.

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The reason why Liberty Prime was/is such a super weapon in the post-apocalyptic Fallout is because pretty much anyone and everyone are lacking in the firepower and capacity to put an end to Liberty Prime, as well as having access to his own substantial ordnance (Eye-Laser and Mark 28 Nuclear Bombs).

The Enclave were lucky enough to be in possession of an old US orbital platform to counteract Liberty Prime. China, in a Pre-war setting, would've been very capable of destroying him via a devised countermeasure of a similar kind.

Also, it's important to note that the SOLE purpose of Liberty Prime was purely to be used to liberate Anchorage. For this (despite the hefty artillery we see in the Anchorage simulation), he was likely the perfect candidate, as China was fighting on the "away team", and possibly had no ability to devise an effective countermeasure (in Alaska) before Liberty Prime had done his job. Despite this, if Liberty Prime had been used to invade China, I have absolute confidence he would've been annihilated.

^We know China indeed had control of said Heavy artillery though, not only because of the slightly unreliable account of the Operation Anchorage Simulation, but also a first hand account from Elliot Tercorien, a medic who spent the day before he was abducted treating those wounded by "heavy artillery bombardment from the mountains"

Even then we know Prime can tank artillery because both the Enclave and the Minutemen use artillery. In 3 Liberty takes the artillery used by the Enclave like it's nothing. In 4 if you kill the Brotherhood after finishing building Prime, he will survive both the Minutmens artillery bombardment and the Prydwen crashing.

^And yet he is killed by an orbital bombardment of similar calibre.

Bethesda were very inconsistent with Liberty Prime's actual capabilities as seemingly missiles shot from air-to-ground are more capable than missiles shot from the ground whose trajectories are incredibly similar, as we see that much.

We also see that the missile sizes are identical, and it's never indicated whether Bradley-Hercules, Highwater-Trousers or Kovac-Muldoon have special missiles, only that they have them. Either way, whilst pretty much impossible post-war (without pre-war superweaponry), in a pre-war setting the paradigms on accessible weaponry are a little different.

I'm confident that if the Enclave in a post-war setting can kill Prime, China could've in a pre-war setting.

^Its not just "air launched" it's from orbit.

The speed from re-entry makes anything a hundred times worse at minimum. Just a 20 foot asteroid for example can wipe out a city.

Just outside of our own atmosphere is a little different than an asteroid at constant velocity in space. 😂 It's not just re-entry that plays a part in orbital impact.

I'm not going to argue with you, you know exactly what I'm talking about as you haven't actually refuted as to whether China is in a better position than the Enclave, yet have nitpicked my Bradley-Hercules point. If Liberty Prime can survive Fat Man shells or the impact of his own Mark 28 Nuclear bombs, an ordinary missile shot from space hitting the ground around him is a little different, yet it destroys him, hence the inconsistency. Also, impact has an effect if it directly hits him, but the payload of the missile stays the same.

Liberty Prime is not invincible, such has been shown by his first death, China could've counteracted him and he likely would've perished. If not for the weird invincibility surrounding a typical and rather logical plot death, I would agree with you. By your logic also, Liberty Prime would not have perished in the Institute ending if he could survive the Prydwen falling on him. As I said, Bethesda's inconsistency.

Kind of makes you think how overhyped Metal Gear is. "The missing link between infantry and artillery" plods onto the battle field one cumbersome step after another before being unceremoniously pummeled into the dirt by an orbital bombardment.

^^I think the reason he didn't survive the Institute ending is he doesn't have full power, or independent power for that matter.

At least that's my best guess.

He isn’t built in the railroad ending. He is incomplete in the institute ending, but fully built and walking around in the Minutemen ending?

^Actually he isn't built in the Minutemen ending either.

You have to do the Brotherhood ending, then turn on them with the Minutemen for him to be there.

He probably would have been bombed from orbit, just like he was in broken steel. Win one otherwise impossible battle for the US, never useful again.