I bought a Macbook with German keyboard layout in Germany. Can I change it to U.S keyboard?

Please make an appointment at the Apple Retail Store - Genius Bar and take it in for service. They can replace the keyboard. You can also try changing the selected keyboard layout using Language & Region preferences.

While you can change the language used for the computer and therefore the keyboard, You would have to change the keys on the keyboard itself to get it to english. https://support.apple.com/kb/PH11251?locale=en_US https://support.apple.com/en-us/HT201794

The software layout is changeable by adding support for US English in

System Preferences > Language & Region

Once you have made that change, if you find the graphics on your key caps are inadequate, a sharpie marker can fix that in about 1 minute at very low cost.

Look thru this. http://www.macworld.co.uk/how-to/mac/how-remove-move-swap-replace-keys-mac-34626 13/ You would need to go online to find the keys you need to replace. You may not need to replace all keys . Just the ones that do not match the English or American versions.