Russia’s and America’s supersonic rockets

I have several books that give a number for the speed of light as being at least 300,000 kilometers a second many times faster if not infinitely faster than sound at a mere 331 kilometers a second. An online estimate of the distance between Russia and the U.S. is given as 8,638 kilometers; so if I correctly understood a media account of Mr. Putin’s recently announcing Russia’s possession of an impossible to defend against rocket capable of flying 20 times the speed of sound I must assume that Mr. Putin’s rocket could travel 8,638 km in less than 2 seconds, for 20 times 331 km. a second(sonic speed) times 20 is 6620 2,000 km. less than the distance to the U.S..

When I did an online search about supersonic rocket weapons I found numerous articles about both America and Russia testing weapons that travel 6 times the speed of sound but no velocity above that speed is mentioned.

The thought that brought that Putin 20 times supersonic velocity to mind caused me to imagine possible consequences of that speed such as an increase in mass and of course its near instantaneous delivery.