“Uncle Sam’s Motorcycle Club” is a backronym (back acronym) of “USMC” (United States Marine Corps). “Uncle Sam’s Motorcycle Club” has been cited in print since at least September 1993.
 
Other backronyms of “USMC” include “Uncle Sam’s Misguided Children,” “Uncle Sam’s Mountain Climbers,” “University of Science, Music and Culture,” “Unlimited Shit and Mass Confusion,” “U Suckers Missed Christmas” and “U Signed the Motherfucking Contract.” Popular “Marine” backronyms include “Muscles Are Required, Intelligence Not Essential” and “My Ass Rides In Navy Equipment.”
         
 
Google Groups: alt.fan.dan-quayle
Lest we forget: THE IRAN-CONTRA SCANDAL
Don McGregor
9/16/93
(...)
Libya claimed a region of international waters, and threatend US ships exercising their right to navigation. Freedom of navigation is _always_ an excellent way to invite a visit by Uncle Sam’s Motorcycle Club. 
     
Google Groups: comp.sys.ibm.pc.games.flight-sim
WB: Why the F’ing Pigs hate dog3
Patrick McGarvey
7/30/96
(...)
Hmmm Free, I thought once you joined “Uncle Sam’s Motorcycle Club” you were always in wether you were an active member or not 😉  Kinda like the ‘Cav, once a Cav Puke always a Cav Puke !
 
Kawasaki Motorcycle Forums
sihing_steve 
01-27-2006
Do you Belong to Uncle Sam’s Motorcycle Club?
All,
Just curious to see how many Marine Corps vets we have as members. I myself was in (U)ncle (S)ams (M)otorcycle (C)lub active from 91’-95’ and IARR until 99’.
   
Twitter
We Make Marines
‏@Jar_Heads_USMC
USMC
Uncle Sam’s Motorcycle Club
12:00 PM - 11 Jan 13
     
X Marks the Scot Forum
Military Rivalry Humor
flyrod6057
27th February 13, 06:00 PM
Marine:
Muscles Are Required; Intelligence Not Expected.
 
USMC:
U Suckers Missed Christmas
or
Uncle Sam’s Motorcycle Club
or
You Signed the Motherlovin’ Contract**
 
Twitter
(OIIIIIIO) Don3 KCCO
‏@dorstis
First I joined the Marines, and now I’m a part of the USMC, Uncle Sam’s Motorcycle Club! I love my bike! pic.twitter.com/hrUzYJlNJq
10:19 PM - 16 May 13