I have to agree with olahaldor.
But i also want to add that if you are really interested in american mod, you should think of doing one yourself. This is just a matter of patience and motivation with every tutorial/guide/etc you can find on internet. I have learned how to make a 3d model and a texture from scratch to help the only other modder who was working on French material for train fever. Just find something fairly easy to start with, don’t hesitate to ask for help on the TF.net forum.