Good question. I can only speculate why immigrants often dropped certian styles of barn after settling into their new territories.
Perhaps a combination of tehnological advances and environmental factors are behind barn evolution. Here in New England, in the early days, the "English Barn" soon gave way to the gable-entry "New England Barn."
As many know, expansion and serviceability were problamatic with the side-entry English barns. A center isle w/ a door at each end allowed a wagon to reach all areas of a New England barn even if it was expanded (wich was done by simply adding bents to the rear). And w/ two doors, no need to turn the wagon around to exit.
America expanded too and farms grew. Sheep farming gave way to dairy here in Maine, which required ever-bigger barns w/ larger haylofts, etc. Steeper roofs, longer buildings... Doors no longer swung open, but slid on tracks because you didn't need to shovel as much in order to slide a door open in winter.
The introduction of sawn stock may have also played a role in barn design. Those mammoth anchor beams come to mind. Ease of construction w/ sawn stock maybe got rid of the anchor??... Why hew a anchor beam if you didn't really need to...
The open "post-free" space the anchor beam afforded might have become less important as well. I don't know much about why the Dutch built this way.