Germans are direct. They say what they mean. And they mean what they say. Germans do not use euphemisms to soften a message. They believe in using unambiguous language and getting to the point. For Germans direct communication is honest, transparent, efficient. Being direct reduces the risk that people will not understand each other.
Americans approach important topics carefully. Euphemisms help to communicate uncomfortable messages. Ambiguity can be helpful. Depending on the sensitivity of the topic, Americans will address it indirectly. In the American context indirect communication is considered both polite and effective. Most importantly it maintains the dialogue in order to deepen it.
For German ears Americans seem to wrap their messages in wads of cotton. As non-native speakers it is difficult and time-consuming for them to interpret statements which are carefully worded. And since euphemisms and figures of speech are context-related, Germans often have difficulty decoding them.
Germans can come across as impatient, impolite, hard. Americans can quickly feel uncomfortable. This hinders more than helps communication. In some cases, Americans will avoid contact with Germans who they (mis)perceive as being too direct, and undiplomatic.
Advice to Germans
Pay close attention to the differences between how Germans and Americans communicate. Use a softer vocabulary. Approach important topics more indirectly. The most important points do not have to be addressed immediately. Establish rapport with the other person, even if it is just a few sentences.
Clarity can be communicated via nuance, also. Americans pay particular attention to nuances. And remind your American colleagues every now and then that English is not your native tongue. That will be a reminder to them that your style of communication might be different. And that the differences are cultural, not personal.
Advice to Americans
Germans communicate with you in what for them is a foreign language. Be thankful that no one has asked you to communicate in a foreign language. Addressing complex and sensitive topics in a nuanced way is very difficult for any non-native speaker.
Therefore, expect German directness. It has its strengths. You know where they stand. For your part, be frank. Get to the point more quickly. And remember, if you don‘t understand something, or if you sense that Germans don‘t understand you, address it openly. Rephrase with other words what each party has said.