Well, both were political decisions and nothing wrong with them.
The US left Vietnam because the fight there was more and more pointless. But certainly it wasn't a sign of weakness. After all the American intercontinental missiles were as deadly and accurate as ever.
They lost a battle but the simultaneous detente with China showed the Soviets their place.
A battle was lost but shortly afterward the Soviets were losing one political battle after another anyway.
France still existed after the armistice, and both the UK and the US were maintaining friendly relations with her.
There is nothing wrong with admitting defeat after a good fight. France asked for an armistice after the best French armies were destroyed, after the fight had become pointless, after the defence of her territory and the civilian population wasn't possible anymore.
Exactly as the American soldiers during the battle of Chosin Reservoir.
Maybe it was a mistake but it was their mistake.
But the small France (in comparison with Germany) and millions of her fallen soldiers in both wars don't deserve the "one french rifle never fired, only dropped once" treatment.
The destroyed German planes weren't available over London a few months later.
The first class, prewar trained German soldiers, the destroyed - by the French or simply by wear and tear equipment weren't available in Russia.
Among them the thirteen most modern German Panzer IIIs and Panzer IVs, destroyed in minutes during the battle of Stonne by a single French tank commanded by captain Pierre Billotte - despite being hit by 140 antitank rounds.