I have a patent idea, and searched the US patents. Nothing comes up, but then I searched the European patent office and a similar, but not the same item comes up. Does this matter since I would be patenting in the US? I am totally new to this.
Prior art for novelty and for inventive step is assessed worldwide, so it doesn't matter where the document originated, it has to be considered for patentability.
For patent infringement only the countries your product enters or is produced in matter.
A simple way to think about it is you can only patent something new. If it has been written about before, anywhere in the world in any language, it isn't new. Of course, like everything else about patents, it is more complicated than that.