Americans prefer directness in communication. It is always proper to ask questions if you do not understand something. They are not ashamed to admit what they do know. Americans will assume you understand something if you do not tell them otherwise. Americans are often uncomfortable with silence.
Silence is avoided in social or business meetings.
It is rude to interrupt someone who is talking. Interruptions, however, are common. Do not be surprised if someone finishes your sentence if you hesitate when you are speaking. Americans put a great deal of value on the written word. American law almost always requires contracts to be written out.