The longest train for the us edition is 83 cars and that's using the ace mixed agriculture in scenario planner, and that's including the locomotives, it would be nice to see trains in over at 10k tons, with dpus.
There are consists over 10000 tons and the longest train is actually 100 cars in Sherman Hill. The max consist length of a American freight is limited by memory cuz every single car needs to have their physics simulated and running which takes up memory even when not actively shown in the background