Germans are systematic in their thinking. Complexity is understood only by grasping how its component parts interrelate and interact. For a component part can only be understood via its role within the whole. Germans use theories and models to explain complexity.
Americans are particularistic in their thinking. They prefer to break down complexity into its component parts, in order to focus on the essential parts. Americans are skeptical of theory. Unless it is based on empirical evidence. Facts and experience are more persuasive.
Facts and experience, without an understanding of the big picture, do not persuade the Germans. To concentrate on the key variables often means to misunderstand or to overlook other important aspects. Americans are often judged to be over-simplifying and superficial.
The German inclination to paint the big picture, especially with the help of theory, can make a professorial and arrogant impression on American ears. German comprehensiveness can come across as long-winded, overly complicating and impractical. Americans react impatiently.
Advice to Germans
A wholistic approach is fine, but be careful not to get tangled up in theory. Warn your audience when you need to go into detail in order to get a particular message across. Leave out facts and factors which are not pertinent.
Do not be comprehensive for the sake of comprehensiveness. If Americans need more supporting information, they will request it. Anticipate those questions. Have the data ready. Questions are a sign of interest, and not that you are unprepared.
Advice to Americans
Take the time to explain the analysis which led to your conclusions. Your German colleagues want to know the what (statements), the why (reasons) and the how (methodology).
Go into much more detail. Include facts and information about various factors. Germans rarely save information for the question & answer part of a presentation. Provide it up-front. In the German context, the fewer the questions asked during Q&A, the more persuasive the presentation.