After all, if America’s military thinkers all believe if America fought China it would inevitably result in mutually assured destruction - then American security guarantees for Taiwan lose all credibility.

Seems a sufficient number of satellites in a particular orbital altitude and inclination would be required to create a self-sustaining cascade.

Even then, the Delta-V of tens to hundreds of m/sec to for violent intercepts seems unlikely to eject debris into different orbital regimes; e.g., it takes nearly 4km/sec Delta-V to move from LEO to Geosynchronous orbit. So, totally Kessler-Syndrome-destroying the LEO orbital range would still leave GEO orbital range available...?

Russia have already attacked subsea cables, openly assassinated targets in many countries, shot down civilian airliners, made multiple drone attacks in Europe, and more. They go for plausible deniability and/or exploit western politicians' desire to avoid conflict and "not escalate" on their watch (and nevermind western politicians already craven to them from the current US President to other parties including AfD, French National Party, etc.).

It is entirely plausible this will escalate to Russia taking out a few satellites, with either kinetic or directed-energy weapons, and the need to replace them. Indeed Russia has been observed testing such systems in the recent years.

There is no need to assume nuke use at all for something to get to the stage of taking out satellites. Taking out satellites with kinetic or energy weapons would definitely leave millions of graduates alive.

If GPS goes down, most of our communications will go down. A lot of other stuff falls from there. I suspect we'd be OK after a brief adjustment, but it would be very disruptive.