Mark Carroll's Journal

The UK's been pretty permissive for many decades, WWII helped encourage positive attitudes toward it and really not much has changed since the early 1980s and it was already largely fine before that. The US saw some positive SCOTUS outcomes about it in decades after WWII but even into the 1980s the State Deperatment was still looking suspiciously at Americans acquiring foreign citizenship to see if their US citizenship should be removed. By the 1990s I'd think they should have been fine though, the State Department got more relaxed. (Spiro's At Home in Two Countries has detailed background.)