Personally, if I stuck to a rigid arrangement of columns, then I'd leave a column blank when entering Welsh place names. Thus, settlement would be column 1 in both cases, county could be column 2 in both cases, country (Wales or USA) would be column 4 in both cases, while column 3 would be blank for Welsh names.
Don't get tied up in the different sorts of counties - you should only need one in each place name.
Personally, I don't stick to column arrangements that match across different countries - I just try to be consistent inside each different country. (Some say Ireland needs 5 columns, for instance, which I only found out after creating hundreds of 3 part English and Scots places... )
Your biggest problem with Welsh names is whether you want to use the English or Welsh spellings! That really does get confusing as I found out recently.