Why do windows in American houses have those white strips It blocks the line of view and makes the windows look small?

The white strips you are referring to are called mullions (vertical) and transoms (horizontal). In older windows, the panes of glass were smaller, because there were not simple and cheap methods to manufacture and support large panes of glass. To make windows that were larger than the individual panes of glass they were grouped in a larger frame or sash, and separated by mullions and transoms.
Some modern buildings use small panes of glass to copy older style buildings, and because it is now cheaper and more efficient to produce larger windows, sometimes fake mullions and transoms are stuck onto windows to copy the older look. Real mullions and transoms can add strength, support and security, but not if they are thin and small. Fake mullions and transoms add nothing, and arguably detract from the appearance as well.