“Sure you can trust the government—just ask an Indian” is a saying that has been printed on gift items such as bumper stickers and T-shirts since at least 1998. The authorship of the saying is unknown.
 
“Any man who thinks he can be happy and prosperous by letting the government take care of him, better take a closer look at the American Indian” is a similar statement that is incorrectly credited to American automaker Henry Ford (1863-1947); the statement has been cited in various forms since 1950.  Another joke about “asking an Indian” is “Illegal aliens have always been a problem in the United States. Ask any Indian.”
       
“I trust the government to lie about everything” is a related saying.
 
   
16 July 1998, Charlotte (NC) Observer, “The Outfront Guy’s Diary,” Living, pg. 4E:
Sure you can trust the government. Just ask an Indian.
   
Sports Illustrated
July 02, 2001
Wahoo Mcdaniel
He was a flamboyant footballer and a wacko wrestler. Now he just hopes to stay alive long enough to raise his son
Mike Shropshire
(...)
McDaniel, who retired from pro wrestling in 1995, drives a ‘95 Dodge Ram pickup with a feather arrangement dangling from the rearview mirror, a symbol of his Native American heritage, and a sticker on the bumper that reads SURE, YOU CAN TRUST THE U.S. GOVERNMENT. JUST ASK AN INDIAN.
 
Google Books
Breaking the Limit:
One woman’s motorcycle journey through North America
By Karen Larsen
New York, NY: Hyperion
2004
Pg. 314:
There were also the statement shirts: “Sure You Can Trust the Government . . . Just Ask an Indian,” “Bikers Are Tired of Dying for Americans’ Right to Drive Like Assholes,” and “I Remember When Motorcycles Were Dangerous and Sex Was Safe.”
   
Google Books
Travels with Max:
In Search of Steinbeck’s America Fifty Years Later
By Gregory Zeigler
Salt Lake City, UT: Blaine Creek Press
2010
Pg. 146:
I recalled seeing a bumper sticker on an older RV, “Sure you can trust the government—just ask an Indian.”
 
The Huffington Post 
Tim Giago
Divide and Rule Was the Unwritten Rule of the Indian Agents
Posted: 06/03/2012 6:21 pm
The old saying goes, “If you think you can trust the government, ask an Indian.”