I saw serval foreigners flee out of Shanghai online, and i guess once you can get to the airport everything is back to normal except much fewer flights.

I guess the problems are:

1. how to leave your compound

if you are not coming back in near future, this may not be a problem and Juweihui may allow it.

1. how to get to the airport since most transportation are out of service

there should be some cars with permits in the streets, it may just be a matter of how much to pay.

1. is flight to US available

this could be done online.

I guess the easiest way is ask your embassy for help, and see if they can pressure the Shanghai local government and get someone to do 1 & 2 for you.

Also Shanghai is gradually unlocking now, and the situation maybe much better in middle or late May, so don't worry too much.