The same thing that's always prevented nuclear-armed countries from going to war: https://en.wikipedia.org/wiki/Mutual_assured_destruction
It is time for the hammer now.
For one their are no explosions, or people with guns. On mars you don't have to worry about people trying to steal your shit because it's valuable (or "necessary for the national defense"), and you don't have to worry about being collateral damage during the war.
On mars there aren't earthquakes, hurricanes, tornadoes, mudslides, tsunamis, floods, volcanoes, lightning strikes, forest fires, and basically any other natural disaster that I missed except sandstorms. When you build a static structure on mars you can expect it to last basically forever, when you build one on earth it has a relatively short halflife. When your static structures become extremely valuable and difficult to replace because you need them to grow your food and you don't have the manufacturing capability to build more, I'd rather be one mars.
On mars you can reliably avoid radiation by putting enough "stuff" (water, soil, whatever) between you and the sun. On earth after a nuclear war it would be coming from everywhere exposed to the atmosphere (in the shortish term).
On mars you get to plan for the hardships while the pre-nuclear-war earth manufacturing base is still functioning. On earth you don't know when the nuclear war is going to happen, or what portions of the earth it's going to glass, so that becomes much more difficult.
On the downside, the martian atmosphere is actually deadly to humans (since it's nearly a vacuum), while the post nuclear war atmosphere is likely only ... very hazardous. Mars has no native plants so you have to be entirely self sufficient inside your colonies, while the post-nuclear war earth colonies could forage for (mildly radioactive) food in emergencies.
A technological cold war will likely happen, Huawei and other Chinese companies will just continue R&D and manufacturing on their own. In a way, the US is letting go of whatever control they had left and making it easier for them to form their own alliances in this matter. It will just polarize the world more... again, as always.
I'll even venture into complete speculation, and posit that WWIII will be fought over, and largely in, Africa. In many ways Africa represents the last frontier on earth, with great natural resources but largely behind in many areas of development and not 'controlled' by either China or the US. South America would also be a potential hot zone, but it's too close to the US. China has realized this already and is investing heavily in Africa, while the US just in the last decade established Africom. Once the US' focus on the middle easy wanes a bit with oil decreasing in relevance, they'll turn their focus to somewhere else. The only reason the middle easy didn't turn into WWIII is because of the relatively powerful players in the area, including Israel, Saudi, Iran, and formerly Iraq. Large enough to hold their own, but not so large that they individually pose a threat to the US hegemony. That, and china wasn't really a relevant player in the world-war starting game until the 80's or 90's or so, and kind of missed the whole middle east war phase. But they're ahead of the game in Africa, and are establishing control there already. And as China transitions from developing country to rich country, they will, in turn, need overseas territories to vassalize themselves. So, there's my wild prediction, that WWIII will happen between the US and China as primary axis of power, sparked over something to do with Africa, right around the time when oil is no longer the US' middle-eastern siren song that it is today. Maybe in 20-30 years or so. Also around the time that millennials will be in the 'old guard', and have no living memory (on a broad, population-scale level) of how horrific war really is. Boomers had the WWII generation still hanging around to warn them off of WWIII, and they still nearly got us there.
So it seems like either that stick needs to get much more effective very quickly, or probably more reasonably at this point we need to try to de-escalate somehow.
In my opinion there is a very obvious lack of cultural and political integration which is inevitably going to be resolved. One way or another. I don't see a plan for doing it peacefully really being promoted by leaders. Which to me indicates that the leadership and overall awareness of the situation is inadequate. And probably we are going to be totally fucked by this ignorance and stupidity at some point.
It's even a war in the comments section.
I don't think it's safe. How do we really know it can't progress to some kind of overt military activity?
Why are people not more concerned about this?
I get the impression that people think the best way to prevent a war is to keep doing things to hold them down. But that seems to be escalating tensions and not actually limiting them.
What is the plan for getting out of this? I hope that Elon hurries up with his Mars rockets so I can emmigrate before the whole planet turns into a complete bloody (literally) science fiction nightmare.