The short answer to your first question is probably yes. In general, a German trademark will not protect you in the United States.
When you add in the extra facts, though, it makes it a little more complicated. Because a trademark’s main purpose is to provide outsiders with notice that you have claimed this mark as yours, it’s protection is usually limited to the region in which that notice is spread. So, when you add in the fact that this is a news website that has visitors from the US, then the question becomes whether it was understood in the US that your German trademark was protecting your brand name. I would say it could go either way depending on how large your American audience and maybe whether you targeted the American audience or not.
The easiest way to make sure would be to go ahead and apply for a trademark in the US; this would be the best way to ensure that you are the exclusive user of your brand name in the US. An experienced IP attorney can help you through the process and will usually do it for a small, flat-fee. If you are interested in a free consultation with an experienced attorney then try out. We routinely connect trademark attorneys w/ foreign businesses looking for protection in the US.