Hufflepuff Common Room
Answer: RIPOSTE
Each of these acronyms has had one word changed. Figure out the changed word and index into that with the given number to spell the clue phrase PARRY FOLLOWER, yielding the answer RIPOSTE.
USAPITRIOT (5) = Uniting and Strengthening America by Providing Inappropriate Tools Required to Intercept and Obstruct Terrorism
TGIM (5) = Thank God It's Monday
EWL (4) = Extraordinary Wizarding Level
TS;DR (4) = Too Short; Didn't Read
CMAO (3) = Crying My Ass Off
IAQ (3) = Infrequently Asked Questions
MASD (2) = Mothers Against Sober Driving
PETV (8) = People for the Ethical Treatment of Vegetables
COLBIRT (8) = Combined Operational Load Bearing Internal Resistance Treadmill
FTL (2) = For The Loss
YOLT (2) = You Only Live Twice
NAAWP (5) = National Association for the Advancement of White People
WFFs (3) = Worst Friends Forever