Weren't huge numbers of people disillusioned when we didn't win the Korean War? And before that, weren't huge numbers of people disillusioned when we didn't conquer/liberate Canada in the War of 1812?

E.g. Wikipedia:

Harry S. Truman[edit]

In April 1951, President Harry S. Truman fired General of the Army Douglas MacArthur. Congressional Republicans responded with numerous calls for Truman's head. The Senate held hearings, and a year later, Congressmen George H. Bender and Paul W. Shafer separately introduced House bills 607 and 614 against President Truman. The resolutions were referred to the Judiciary Committee[9] which, being run by Democrats, sat on them. However, the US Senate held extensive hearings on the matter.

Lest we forget, MacArthur tried to expand the Korean War into a war with China (which by treaty would have also involved the USSR).

And before that there was the "Who lost China?" battles.

Lots and lots of people on the Right have been convinced that the government can't be trusted, the government is filled with spies and traitors, the government wants to enslave every "real" American...

There's lots more polling now, and lots more hearing about polling now. I dunno if opinions among a substantial fraction of the population really changed in a long-term way, and if it has, whether it can be shown to be the result of Vietnam or Watergate or Iran-Contra or whatever.

NORC GSS - Can People Be Trusted? (1972 - 2014)

FWIW.

Cheers,
Scott.