Chariots were a symbol of the powerful empire. They were good platforms for a general or king to stand on and be seen, and they looked very threatening when they charged forward covered in spikes and blades. Very much a tool for scaring disorganised forces and flaunting the wealth of the king, which is why they were sent after the slaves in Egypt. They could also pepper the enemy with arrows and even drop off a few soldiers, acting something like personnel carriers, but their nifty uses were strongly countered by consisting of a cart tied to a couple of horses racing across a battlefield.
They would flip over if they hit a rock or hole, get bogged down in mud, lose control on slopes, have poor manoeuvrability, and leave the horses vulnerable to nearly all the attacks, which would also flip the chariot. In their time they had a role that they filled, but they were superceded by either agile cavalry or even more lumbering elephants.
The only lasting legacy was chariot racing, the incredibly lethal racing sport where they travelled in a circle on a flat track.
If an army does not have the equipment, training or strategic skill to counter them in any number of ways (not making the battlefield a perfectly flat plain, stepping to the side when they charge, pointing weapons at them...) then that does not bode well for their other ventures.
Judges 1:19 being set after shouldn't mean anything, as the rule "Fight with God and you will win, or else" is long-established by then. When they lost it was because they lost faith or otherwise annoyed God, but in 1:19 they specifically had God on their side helping them win, until they were beaten specifically because of the presence of iron chariots. Chariots were good if used by masterful tactician in perfect circumstances, and iron is as stabby as bronze, but it is odd that a common, severely handicapped weapon of war and a particular material that they were made of were enough to stop the army and/or divine being that had just conquered half the Middle East.
To me, the most intriguing part is that the Bible includes this defeat of God. I mean, of all the things to get purged and mistranslated away, this thing stays in?