It is unequivocally one of the greatest military victories ever. The significance of the "rapid dominance" theory of war fighting, as well as force-on-force engagements, specifically within cities (likely MORE significant than "rapid dominance")
Under the presumption you are actually interested, and not just running your mouth;
An invasion of a country and the toppling of its government is not easy. It was expected to take a long time with high casualties. The logistics, the capturing cities, et al is a nightmare. Iraq had one of the largest armies in the world, with fiercely loyal units that were positioned to take advantage of long supply lines.
It was concidered highly likely that the methods employed would fail and the invasion would fall apart and require massive reinforcements to push through cities, as well as backtrack to cities that were bypassed.
The significance is doctrine. The "coalition" (ie US and British forces) toppled a government and concluded major hostile action in 21 days against a military that was a million man strong, and included urban warfare. Can you point to ANY invasion against a prepared enemy that was concluded in 21 days? Ever? In the history of warfare (even ignoring the urban combat element)?
Seriously... can you?
I highly doubt it. The battle for Hue took 26 days of major combat operations... for one city. The invading force lost 700 people out of 4,400 casualties. After the enemy had 1 day to entrench.
In total, against a force of a million man army, and fighting through entrenched forces in urban areas, while supplying advancing combat forces across 500 miles, the invading force lost 196 people with less than 1000 casualties, and won in 3 weeks time.
Basically, the invasion force was a light force that relied on "shock and awe" and new urban force on force doctrine, in the hopes of limiting civilian deaths as well as coalition deaths, because typically, invasions are a fucking mess. It was a shocking success.
Logistically it will, without a doubt, be taught for generations. Tactically, the methods the invasion force used to in fighting, and discouraging the enemy will be taught for generations. Strategically, the method of preparation, and advance on Baghdad will be taught for generations.
It worked so well, that NO ONE IN THE WORLD, including the people who developed the doctrine, had predicted how well it would fast and totally it would work.
It worked so well that we sent huge numbers of troops home at the conclusion of major hostilities, and most of our force never saw any combat. It was later that those dumbfucks realized when you win, you now own that shit and have to keep it stable, but we had already sent a good portion of the force back, left no one to even guard the banks or museums, and to top it off, disbanded the police and military...and replaced them with nothing. As though a transition between occupation and invasion would magically happen.
But, yeah, it was a pretty amazing, historically speaking, victory. Right now in popular culture it is conflated with the occupation, but have no doubt that every military in the world is trying to figure out how to reproduce a win of that swiftness and magnitude with such a low body count.