ASATs exist, but trying to blow up a couple hundred satellites WILL be a pyrric victory. Most countries don't like self-destructive victories. Maybe the US would be crazy enough, since it co-created the Mutual Assured Destruction doctrine.
I already described the Kessler syndome (
https://www.space.com/kessler-syndrome-space-debris), but let me try again. Each blown up satellite creates a small cloud of shrapnel. One satellite's worth of shrapnel might not hit anything, but each one you blow up creates another debris cloud that endangers more satellites. Each satellite hit by debris also is partly or completely turned onto more shrapnel. Pass a certain threshold and it becomes a self-sustaining chain reaction. This turns low Earth orbit into a blender where no satellite can survive for long. So, NO COUNTRY will get to have spy satellites, weather satellites, communications satellites, navigation satellites, science satellites, or space stations in low earth orbit for at least a few decades.
For higher up, a single cloud of shrapnel in a retrograde equatorial orbit where the geosynchronous satellites are parked will destroy most of them in 12 hours. Survivors get a 12 hour reprieve until the cloud comes around for a second pass.
The horrifying thing is that we're already in danger of a Kessler Syndrome event happening spontaneously due to the amount of junk already in orbit. This is why space agencies around the world are working on orbital garbage collection devices. If they could cooperate instead of being influenced by pathetic war-porn novels, we'll have a much better chance of preventing this from happening.
Edit: I just accidentally tripped over a pic of what a small piece of space debris can do. No, you don't have to shoot it that fast. All you need is two different orbits intersecting to get some amazing velocity differences.
But, just to humor you and the author of this sick fantasy let's pretend that Chinese ASAT weapons use magical disintegration ray cannons so there's no danger of a Kessler event. Now tell me how many spy satellites and military communications satellites the US has and how they can all be disabled within the span of a few minutes? Oh, and don't forget that US military and civilian intelligence agencies like to keep secrets not just from China, but from each other too.
But by the lame power of deus ex machina, the Chinese somehow get hold of the non-existent master list of all US spy satellites and military communications satellites and somehow manages to set up giant emplacements of disintegration ray cannons around the world so that all of these hundreds of satellites can be taken down in 5 minutes. Then what?
The US military and government switches over to Starlink and other friendly comsat constellations. Civilian mapping satellite companies provide live feeds from their satellites. Allied natiions provide access to both government and civilian satellites.
But, this story being far above average in forcing irrational storylines to continue lets China disintegrate THOUSANDS of other satellites in just a few minutes.
The Secretary of the US Navy hangs his head and says "I have no way to talk to our submarines." His second in command says "Except for the extreme low frequency system." The Secretary replies "Oops, I forgot about that."
"What about our military bases in the Pacific?" asks the President.
The Chairman of the Joint Chiefs of Staff replies "Before we lost Starlink most reported in. Each was hit with ten hypersonic missiles with large conventional warheads. We've got radio communication back with 8 of the large bases so far. The smaller ones are out of operation, but whoever planned attacks with only 10 missiles against our larger bases was a complete moron." As he finished the sentence, a bolt of lightening struck the chairman, killing him instantly.
A distant sounding disembodied voice with at Australian accent was then heard saying "Stop messing with my story. China has to win this or I won't be able to lobby for bigger military budgets. Even more importantly, if China doesn't win, I won't be able write a sequel where Australia saves the day and conquers China."
****
If you want to see a real war, there are a number of them in progress right now.
I think you should scroll up and read that "Australian Way of War" article again. You should be VERY concerned that the US isn't just pushing Australia into trade "wars", but is pushing Australia's military into closer and closer encounters with China's military.
If the US and China went to full scale war, the US would be throwing as many Australian, Japanese, and South Korean troops as possible to reduce US casualties just to make the war more palatable politically back home. If Australia is the only allied country involved in a flashpoint that leads to shooting, can you be confident of how many Americans will be sacrificed to save Australia?
Australia would be a pretty pathetic staging area with Japan so much closer. Even then, this magical Peal Harbor type preemptive strike is a pure war-porn fantasy. There's NO WAY to disable that many satellites that quickly and to stop all other means of communications. There's NO WAY to thoroughly disable large military bases with one small volley of conventional missiles.
If this was possible, the US has about 3 times China's military budget. Why hasn't the US taken down all of China's satellites (without losing ALL satellites), sunk all its warships, and deployed Baron von Munchausen to take care of any pesky details that were forgotten? Quite simply, it's because the only way to be that thorough within the laws of physics is to use WMDs in a preemptive first strike. Thankfully for the world, the US still has enough sanity to realize that the price would be far too high.
Instead, the US wants a long simmering war, nowhere near its own coasts, with plenty of "friends" to serve as human shields for US troops. China doesn't want to play that game. China's long game is simple. Keep TW aware that China has a red line and do everything possible to keep TW inside of that line. Eventually, tides of opinion will shift, 1C2S agreements will be signed, and China will be reunited.