Universities still closed and students work online in USA ?

No. Starting the spring term or winter quarter a week late, canceling spring break but replacing it with virtual catch up periods. 

Most courses will be online , but there are some courses that cannot be taught online. 

Staff may not be working on Fridays at all and may be online only between 9 am and 3 pm.

Each University and college is different in the United States. I am using two different universities in 2 different states to base this?answer on. My best and closest friend is?a full time faculty member at ONE of them . She's going crazy because Orleans parish is in in stage 3 lockdown while Jefferson parish is in stage 2 lock down. She can't teach her anatomy & physiology labs because the university is in Orleans parish. 

Universities are NOT closed even if most of the courses are online or hybrid. Some courses or parts of courses cannot be taught online. How to dissect an animal or a human cadaver has to be hands on. Same with how to create a?slide or thin section. 

Some are, some aren't. Mine is doing a combination- some online courses, some hybrid, some meeting in classrooms. 

At many universities, yes.