Germans are systematic in their thinking. Complexity is understood only by understanding how its component parts interrelate and interact. And a component part can only be understood via its role within the whole. Germans use theories and models in order to grasp complexity.
Americans prefer to break down complexity into its component parts, in order to focus on the truly essential parts, so that action can be taken. Americans are skeptical of too much theory. Instead they focus more on facts and empirical evidence (experience).
Facts and experience, without a convincing description of the big picture, are simply not persuasive to Germans. To concentrate on the key variables often means to misunderstand or overlook other important aspects. Americans are often judged to be superficial and over-simplifying.
The German inclination to paint the big picture, especially with the help of theory, can come across to Americans as professorial and arrogant. Comprehensiveness is frequently misinterpreted as long-winded, overly complicating and impractical. Americans react impatiently.
Advice to Germans
A holistic 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 (message), the why (reasons) and the how (methodology). Provide greater detail.
Include facts and information about various factors. Germans rarely save information for the question & answer part of the presentation. Give them the information up front. In the German context, the fewer the questions during Q&A, the more persuasive the presentation.