Here is how you can type French diacritics without switching to French keyboard.
You can switch to French keyboard if you don't want to type "alt" + four figures each time you have to write a French diacritic.
|If you want to write this French letter :||you need to type this letter on your US keyboard :|
|â, ê, î, ô, or û||[ + a, e, i, o, or u|
|ë, ï, or ü||SHIFT [ + e, i, or u|