Obvious parallels between Vietnam and Iraq:

Both countries ruled by one-party systems that had taken control through non-Democratic means. This was true of both parts of Vietnam.

Outside involvement primarily by the US, with enough other players to give the illusion of a coalition.

Significant, if not majority, opposition by the American people.

Generally a military success but a political and socioeconomic failure.

Government unwilling to provide complete and uncensored facts regarding all facets of operations (and I'm not talking about ongoing military operations, which cannot be entirely open while there are going on.

Failure to have an adequate civil affairs infrastructure.

Failure to have an adequate exit strategy, or even to recognize the need for one.