Since the draft ended in 1973, every few years there "has been talk about bringing back the draft."
It's just that ... talk
If a war broke out that's exactly what would have to happen.
We're talking specifically a scenario where there's a war in the persian gulf and in china at the same time.
In all reality America would probably just walk away, but we never know.
If we got stuck in a Persian gulf war and some sort of Korean/Taiwan fight for an extended period of time they'd need to do a draft.
The US cannot deny Korea/Taiwan and Persian states all at once.
This is sort of the point.
Ukraine is fighitng on home turf, if it were the Americans attacking Russia on home soil we'd have many of the same problems the Russians currently have.
It's not easy to invade a place like Saudi Arabia/China/Korea.
Let we're in a situation where things could easily blow up, and get crazy fast.
Pakistan is also a powder keg at the moment.
Pakistan if you didn't know has as many people of peak war fighting age(18-25) as China does.
If Asian countries team up it's world war 3.
And they all their motivations.
Russia/Saudi Arabia/Iran all rely on oil exports and so they'd love nothing more to shut dow Japan/Europe by cutting off their supply of energy.
It'd be like the 1970s oil crisis all over again.
This would basically be a New kind of Opec trying to take over world energy production.
On the flip side
Korea/Pakistan/China are all fucked and have no future as their economies have all hit brick walls.
China could easily help North Korea invade south Korea, by just supplying bodies.
If a Korean war and a Taiwan war are being fought simultaneously, the US would have to go all out, and if the persian gulf is going to hell at the same time it's all the more wild.

If the Saudis and Iranians work together, they have control over most of the worlds oil that isn't produced by either the USA or Russia.