Hello threeducks1994 thanks for reporting this crashing issue with the Atlas you have encountered, I am sorry to hear the issue occurs when trying to return from Ireland.
How many quests have you completed in Ireland so far and does the crash with the Atlas still occur, after completing a few more main Ireland missions?
Can I also ask you what your current recorded play-through time is, so we can check how many hours you have played and how much memory you have installed in your computer?
This support article contains some of the most common fixes for crashes and it covers permissions, hardware, software, and corrupt files, that could potentially cause this. Please run through ay steps listed you have yet to try. Should these steps not resolve this issue for you, it will at least help us rule out a few potential causes of this issue. >
https://www.ubisoft.com/help?article=000061047
Please get back to us when you can on the questions above, as well as letting us know what happened after trying our troubleshooting steps. If you can also upload your save file to our cloud, it will help us investigate also, thank you.