My only experience is riding in England and Ireland. It didn't take long to get used to riding on the left side and many roads I was on in Ireland were small roads, without much traffic. However, there are no shoulders on the roads.

Riding in Cambridge took a little more getting used to, but it's a very cycling-oriented city so drivers are very used to dealing with cyclists. It helped to get some guidance from my daughter and her boyfriend at first. We didn't ride it London but there were many cyclists there. Still, it looked a little bit scary with all the traffic.

Riding on main streets in Dublin would probably be a little more challenging.