Unfortunately you can’t hide your Facebook username in profile url because username is also related with your url at all. You can’t assign a random url for your profile. So you will not able to change url different than your username. Once you assigned a username for your account, you will not able to turn it into the profile ID too. So there will be no chance for you to make the profile url different than user name.
See Also: How Do You Hide Your Name on Facebook?
Can You Hide Facebook Username in Profile URL
You can’t hide the username in Profile URL as we have described above. If you don’t want your account because of the username, you can delete it and you can get a new account. We recommend you to not to assign username to your new account for this. Once you want to delete your account, it will be deactivated for 2 weeks. Then it is going to be deleted. You can use your new account after you delete your old one. We recommend you to not to login to your old account because it will be active again if you ever do it. Once you activate your old account, your both account will be in danger because Facebook doesn’t allow multiple accounts.
Contact Facebook Support
If you are looking for an alternative solution, you can always contact Facebook support and learn more about directories. Here is the Facebook Help Center for you. You can find some solutions on here regarding your problem. However we don’t think that Facebook staff will change your url or username to a random one. This is a little bit trying the impossible but you can still get a positive answer from staff. Please let us know if you have any questions.