Germans define realistic as understanding reality. To understand the reality, is to understand how it became so, via its past.
Americans define realistic as understanding the possible, to envision a future. Forward movement often demands moving away from the past.
American visions are often not grounded or rooted in an accurate understanding of the status quo. Americans want to move forward without first establishing their starting point and direction.
Too much emphasis on the present as a product of the past is seen as backward-looking. A vision of the future, forward movement, demands moving away from the past.
Advice to Germans
Provide the historical context. But again, let your listeners know beforehand that you need to tell the full story. Your aim is for all to have a common understanding of the status quo before you can consider how best to move forward together.
Advice to Americans
Try to hold back your natural tendency to jump from the present into the future. Take the time to explain the context of a situation. This will lengthen the presentation. Do your homework and demonstrate that you have done it thoroughly.