Despite what President Trump has declared on Twitter, "opening up" the American economy is not his decision. Quarantine authority belongs to the states. The federal government's powers under the Constitution are limited, with wide latitude given to the states to set policy. The Tenth Amendment says any powers not explicitly granted to the federal government (or explicitly prohibited to the states) are reserved to the states.

Also, National Review does a great job exposing the news media's hypocrisy here:

It has indeed been galling to watch many within the press corps repeatedly ask Trump why he has declined to preempt gubernatorial decisions or shut down grocery stores when he does not enjoy the power to do either. It was galling, too, to watch many of those same voices erupt in indignation when, eventually, he began to talk as if he does.

Source: National Review.