An FAA conversion isn't difficult, just a little expensive.
First, you need to have the FAA ATP flight time minimums.
Then get an FAA class 1 medical.
Do the ATP CTP course (a bit like the EASA MCC).
Do the written exam (requires 1 week study)
Go to sim centre for 320 type rating and check ride.
First get the medical. It is possible to do it in many places outside the USA. The rest must all be done in the USA. You will also need to register as an alien flight student. A regular tourist visa is all you need to enter USA to do a type rating. I know, I have done it.
The CTP course is 5-7 days long and some places offer the written test at the same location. Test prep can be bought online from different websites.
Sim will be 12-16 days in duration.
Costs, CTP around 5k USD 320 type 8-15k USD.
Allow about 4k USD for flights and living expenses while in the USA.
Pan Am aren't the best type rating provider but they do CTP and type ratings at the same place and they have a lot of experience doing foreign license conversions. I know I trained there.