Why is the atomic clock in Colorado?
First of all, there is no “the atomic clock,” the timing signal your receive is actually comprised of data from many atomic clocks. A radio signal is generated by NIST in Colorado, partly because a portion of NIST is located in Colorado. Having a more-or-less centrally located radio source maximizes radio coverage in the continental US. There is also an atomic clock ensemble at the US Naval Observatory in Washington DC, which is the timing source for the Department of Defense.
