The Vietnam war is a clear loss for the US. I'll give you that. It was a mess and a lot of US soldiers died and they retreated
The first Iraq war was a victory, the aim was to remove Iraq from Kuwait and they did it very efficiently, with UN backing, too. The problem some may say is that they didn't follow Saddam into Iraq (I personally don't think they should have).
The second Iraq war was also a victory IMO. They took over Iraq in about 2 weeks. The liberal media backlash held the US back from properly civilising that s**t hole and now look what kind of a mess it is. IMO, when the US decided to invade Iraq, they should have gone all in or not at all. Send the army in and completely civilise the country's infrastructure and remove the native culture at gun point and IMPOSE American, western culture on them (harsh, but f**k it). Or don't go in at all .... The US kind of went half-assed with the plan for post invasion Iraq.
In hindsight, I personally think they should have supported Saddam Hussein, that country needs a strong, no nonsense leader, at least he kept it relatively stable.