Democracy is inherently weak when it comes to war. We are subject to the political pressure that media can bear upon the administration.
When we are united, as in WWI and WWII, we win.
When we are divided, as in Vietnam, we lose.
The enemy cannot beat our military, so they have learned to beat our will via the press and the minority political party.
The sad truth is Americans need hundreds of thousands dead before they will set aside partisanship. I am not sure the Democrats would ever set aside partisanship to defend America.