score:3
Yes it can play negatively. If a consular officer is looking for an excuse to deny you, that is a perfect and legitimate opportunity.
The employer letter with vacation dates and declaration that your position is available for you to resume after your vacation is a very strong tie to the home country (in this case USA).
You could also be approved without the letter, even unemployed people do get approved, however it is a good criteria on which to deny you if the officer so chooses. You can't take chances with visas despite you good immigration profile/history.