Can one-time usage of mdma cause social anxiety for extended periods of time?

Yes, in some: Mdma affects serotonin, dopamine, and norepinephrine, leading to other effects as well. The surge of serotonin can deplete the brain of serotonin -- resulting in negative after-effects like confusion, anxiety, depression, sleep problems, etc. These may last for days or weeks afterwards. It's impossible to know the true or complete contents of what you took, making results more unpredictable.