The way I see it is that the US is a federation of 50 nations. so if he wants to lock down his nation, he has the power to do that.
Well, his city within that nation, anyway.
Democrats have three major problems with President Trump:
1) He is Hitler
2) He is a Dictator
3) He has refused to demand a national lockdown which would force everyone to do as they are told and move about only with his permission.