Is it common in the USA that employees just disappear without getting the chance to say goodbye to their colleagues? At most places I worked, people tended to send a goodbye email to everyone@company and got a chance to say personal goodbyes, even when there was a negative reason for them to leave.
Yes it is common when the employee is being terminated. It may depend on the industry, but it's always been like that at the 10+ companies I worked at.
Honestly, I much prefer it to the long notice (sometimes 3 months!) you get in say some European countries. Just rip the band aid and move on. Most likely you'll have a way to connect with former coworkers easily on LI and such.