I struggle to think of a scenario where cross-region transactions would be useful. Why not just pick a primary region where transactions will be carried out for a given piece of data if consistency guarantees are needed?
I guess if your partition time interval was known to be very short, like a flaky ISDN link, it could make sense for some use cases using retries, but then you should just get a better link.
CockroachDB discusses a multi-city vehicle sharing use case where multi-region transactions could be worth consideration, but I'm skeptical:
https://www.cockroachlabs.com/docs/stable/multi-region-use-c...
(Developers and students get all excited about distributed systems, CAP, etc. but as a DBA, network partitions are largely not solvable from both technical and business standpoints. The solutions that do work include using vector clocks, or investing in a very reliable network, which is what Google is doing with dedicated fiber.)