Fact> All countries had gun makers who made very good guns and very poor guns .
You can not make a general statement that one countries guns were better than anothers without factoring in numerous things .

Birmingham gunmakers in the past produced a lot of guns that were to be honest terrible .
Spanish , Italian makers also produced poor quality guns as well as very high quality guns .
Pricing aside , I have seen well made continental guns poorly finished so looking cheap at the same time exceptionally well finished guns that were terrible inside. Some Turkish I have seen are good examples of this .
You need also to consider the materials used , traditions/style of the gunmakers of that country and the market they were made for ie. was the gun meant to shoot a few birds for the pot or to shoot 500 bird drive days on a grouse moor ?
Each must be taken on its merits and comparisons can only be made by comparing guns of similar style and age .