The US would never nuke anyone unless it was nuked first.
Getting back to the original question, most rifles have a muzzle velocity of 600-1100 m/s. To get from LEO to GTO requires more like 2400 m/s delta V. So a lone gunman in LEO can't shoot at GEO targets, even with perfect aim.Movimg on to shotguns, if the DPRK or Iran decided to put 100 kg of buckshot in a 350 km orbit, would there be any way to defend the ISS?
Secondly, while 3000 fps may not be enough velocity to achieve a Hohmann GTO, it may be enough to reach a apogee of 23,000 miles in a Molniya highly elliptical orbit. Need to crunch some numbers to find out. If its possible, a bullet in a molniya orbit would cause more damage to a satellite in GSO due to higher closing velocity.
Generally speaking the terminal velocity of a rifle bullet falling straight down is about 300-320 fps, so a bullet with muzzle velocity of 2700 fps at sea level should see a muzzle velocity of about 3000 in vacuum.
I'm thinking Mike Lorrey's addition of terminal velocity may have been some intuitive response to the addition of the effects of having vacuum in the barrel?So, could we shoot a 30-06 100 miles? 1000 miles? and still kill the target sat.