So the installation of a huge radar array in the Czech Republic radically increases the possibility of a first strike by threatening to blind Russia's early warning radar system for the very few minutes required to launch and land the latest generation of American missiles.

ICBM launches are detected by early-warning infrared satellites, in high-excentricity polar orbits. The observation can't be jammed. The communication of the warning either (it's a narrow-aperture parabolic dish in Moscow probably). The only things that could be trans-horizon jammed are the tracking radars of the anti-missile system around moscow, to minimize the probability that the capital survives (near zero anyway in a real first-strike, it would be the target of a massively saturating attack).

It's impossible, even for the US, to launch a first-strike without the ground-based ICBM's taking off (submarines take longer to warn, very-low frequency comms have low-throughput, and a hunter-killer sub could be stalking them and attacking them in sync).

Therefore, the contribution of the Poland base to the first-strike ability is to provide a launch site for boost-phase interceptors (of Russian ICBM shot from e.g. Ural silos). Note that the "window of execution" is narrow, if not inexistent: although the US are trying to secure the sites today, no boost-phase ICBM interceptor will be available in the next 10 years at least (European defense industries have projects possibly closer to market, but these are low-end, focused on scud-like missiles, with the aim of making good export success in the Middle-East). By that time, Russia will be sailing an entire flotilla of new strategic submarines that the US will probably not be able to stalk.

Pierre