I think you need to be more specific about your credentials. Am I assuming correct:
You have an FAA commercial, multi with instrument privileges? You passed the ATP written, but did not take the checkride?
You are offered a job but need some particular advice.
Does the company require an ATP? Do you have enough hours to obtain an FAA ATP?
If the company doesn't require an ATP, you have nothing to worry about.
If they do require an ATP then go to the US and do a weekend course with ATP (jee, that's not a confusing name in this post) or someone else. Better hurry since your written is only valid for 2 years after passing.