It’s because the US government is merely giving guidelines to states on how to implement containment policies. Each state (as Trump has alluded to) has differen

It’s because the US government is merely giving guidelines to states on how to implement containment policies. Each state (as Trump has alluded to) has different needs, different spread, ect. Some states need stricter containment because the densities are higher in that state. It is then up to the Governors to dictate policy. Also for the federal government to actually enforce containment policies requires the government to enact traditional war-time, and what look like more authoritarian, laws.