Divs are 100% width of the browser window **unless** they are in other elements that restrict their size. In which case they are automatically 100% width of the containing element.
If you are going to have a divs that will be full browser width **but** you still want the content contained (presumably because your want a full width bar or something) then you have to get out of the mindset that “everything is in a single container”.
It’s just not going to work.
The ideal solution is to set up, in effect, rows of sections for the various levels of your page. If you need to have some content inside a defined width then you have to add ‘inner’ divs/containers which have that set width.