Help docs! i had bad breath and a pus in my mouth, can it be due to the crown and root canal?

Many possibilities..: But only a physical exam of the problem with radiographs will give you the correct answer. Cannot possibly diagnose the cause of your problem over the internet. Yes, it may be the root canal and/or crown, but it may not.

See a dentist: In the majority of cases, the cause of bad breath, or halitosis, is the product of bacteria in the mouth. The proper diagnosis is the key to a successful treatment. See your dentist for Halimeter test, diagnosis and bad breath treatment that depends on its cause. Good luck.