I agree that it is a European bike but there are many clues. Things like the bolt sizes and small stampings on internal parts are clues and it does take a lot of research. Taking many good photographs, uploading them and showing them around may be a great help. There are a lot of people viewing these threads and inquiries take time.

I don't know anything about your bike yet but I did some searching on American and British brands and found Columbia and Raleigh models that are close also.