I guess a couple of things need to be said here at this point:
1) Marklin did make American-style trains for export to the American market in the 1920's. These were not just "European looking trains" dressed up a little. They were entirely different tooling, detailing, and lithography. American freight car design was used, giving them very different proportions and details from the European counterparts; the sliding box car doors, brakewheels, ladders, no buffers, American road names and heralds, frame trusses, American-type hoppers and gondolas, and of course the #504 Pennsylvania "Coke Car", which was famously copied by Ives. All these are quite unlike any Marklin-made European goods wagons.
The following photos are a few random American cars made by Marklin. There were several more. These were all Gauge 1 cars. Most of these are pictured with Ives wide gauge (standard-gauge) trucks, which I have temporarily put on them, to run on my layout. To be clear, these were Gauge 1 cars made by Marklin to sell to the American market in the early 1920's, when Ives was still making Gauge 1 trains and Lionel's "Standard Gauge" had not yet become the industry standard. These are being shown to illustrate that Marklin made specifically American trains for the American market. Compare these pictures to any Marklin Gauge 1 Reichsbahn goods wagons, they are entirely different design, proportions, and construction start to finish.
2) The second part of this is that later, in the late 1920's, when Gauge 1 trains were rapidly being abandoned in this country and all the major manufacturers had converted to 2-1/8" "standard gauge", both Bing and Marklin decided that if they were to continue exporting to America they would need to do likewise. Like Bing, Marklin certainly did make and sell Standard Gauge trains, for export to the USA. As mentioned by previous posts in this thread, several well-known, world-class collectors in this country have had Marklin Standard Gauge in their collections.
As an example, the photos below are of my Marklin Standard Gauge American-style New York Central coal hopper car.
There are some close-up photos here, but even these do not show very well, what is quite evident when you have the car in your hand; which is that these are Marklin Standard Gauge trucks, factory installed and never removed or switched. I obtained this car at a Stout auction, it came from the Ward Kimball collection. I also got several of Ward's Bing Standard Gauge cars.
One might suggest that this could have been a Marklin Gauge 2 car, and someone has tweaked the trucks a little to gain the extra 1/8". But this cannot be the case. Marklin Gauge 2 was exclusively European, and Marklin did not make American style cars in Gauge 2, or export Gauge 2 to America. Marklin also stopped making Gauge 2 around 1918 or so. This hopper was made by Marklin in the late 1920's, about a decade after Marklin stopped making Gauge 2 at all. So there is no overlap, and many years in between European Gauge 2 and Marklin's American Standard Gauge.
What Marklin did, as did also Ives and Bing, was to take their American-style Gauge 1 cars that were already in production, and already being shipped to America, and made a new Standard Gauge truck to put on them in place of the Gauge 1 truck. (Personally, I feel that the Marklin cars are more successful at making this transition than either the Ives or Bing. Both the Ives and Bing Gauge 1 cars are quite small, and undersized for Standard Gauge. The Marklin cars are more rubust, and compare in size to Lionel 200 series freight cars.)
Notice that as well as the Standard Gauge trucks, this Marklin New York Central hopper also has original from the factory Marklin hook couplers; these were made to be compatible with the hook couplers used by Lionel on their early cars. It will also hook into Ives and the Marklin Gauge 1 couplers.
For whatever reasons (a lot changed politically, socially, and economically around the end of the 1920's, both here and in Europe), the Marklin American Standard Gauge venture was short-lived – perhaps only for a year or two – so there are not a lot of them out there. Documentation is difficult to find. Also, for obvious reasons, it is not likely that collectors in Europe will see many of these or know much about them. But collect Marklin on this side of the pond for long enough and you will come across Marklin Standard Gauge if you keep your eyes trained to see the different truck.
happy collecting!