In Manhattan I've noticed a huge drop in the number of tourists in the past few days, but what's more interesting to me is the total number of people out and about in central park (and other parks) hasn't dropped much. It seems like most of the tourists you usually see were just replaced by locals. I suppose now that everyone is "working from home", they've got time to take walks in the park and enjoy the nice weather. I've also noticed fewer taxis/cars in general on the roads, which is quite nice.
This, of course, is strictly anecdotal observation, so take it with a grain of salt.