The placement would have to be just right and the explosion done at night as the the sun’s rays on the day side thin out the van allen belts displacing the thickest parts to the night side. The curvature of the Earth also would effect which parts get the strongest effects(the center areas) while the edges would get the weakest. Local anomalies would also cause hit or miss effects. One small yield nuke just won’t do it and the placement would have to be just about perfect and timed with the maximum amount of magnetospheric “support” to get any kind of damage at all. A timed equidistant explosion of 3 or 4 devices simultaneously at just the right places in orbit might cause the feared predicted massive damage but a single device won’t, especially since placement is a variable in terms of predictable results!
Considering the devastating results if it worked, it must be nice to be sure. Are you sure enough for me to bet my children’s and grandchildren’s lives?
With no malice may I reminded you that in April 1942 the best minds in Japan considered that a attack on mainland Japan by American forces was impossible. On April 18, 1942 Lieutenant Colonel James “Jimmy” Doolittle proved them wrong.