Germans are direct. They say what they mean and mean what they say. Germans do not use euphemisms to soften a message. Nor do they "beat around the bush." For Germans direct communication is honest, transparent, efficient. In their view, it reduces the risk of people not understanding each other.
Americans approach important topics carefully. Euphemisms help communicate uncomfortable messages. Depending on the topic's sensitivity, they will address it indirectly. In the American context, indirect communication is considered both polite and effective. It maintains the dialogue in order to then 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 to interpret carefully worded statements. And since euphemisms are context-related, they must be decoded.
Germans can come across as impatient, impolite, harsh. Americans can quickly feel uncomfortable, thus hindering more than helping communication. In some cases, Americans will avoid contact with those Germans (mis)perceived for their particularly direct communication.
Advice to Germans
Pay close attention to the differences between how you as a German and how the Americans communicate. Use a softer vocabulary. Approach important topics a bit more indirectly. The most important points do not have to be addressed immediately.
Establish a little 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 remember to remind the Americans every now and then that English is not your native tongue. That will be a reminder to them that if your style of communication bothers them that it is cultural, not personal.
Advice to Americans
Germans are communicating 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.
So, expect German directness. It has great strengths. Germans will say what they mean, and mean what they say. You know where they stand. For your part, be frank. Get to the point more quickly.
Germans will not take it personally. And remember, if you don't understand something, or if you sense that Germans don't understand you, address it openly. Rephrase in other words what each party has said.