What if the United States congress, and those of the individual states, only had a single house of congress rather than a house of representives and a senate?
Never going to happen.
The otl constitution was a fine balance between the large states, which dominate the house due to population, and the small states that get a hearing in the senate.
Try to make everything rep by pop, and the small states refuse to ratify. Make everything leaning towards the small states, and the large ones refuse to join.
Try to make the same changes now, and the same dynamic happens.
No unicameral congress would be accepted by enough states to exist. If it were tried, the us would still be using the AoC or split up.