"剑可以灭我们的国，但是可亡不了文化" seems ok, but it's better and clearer that you say：刀剑（或许）可以毁灭我们的国，但是可毁灭不了（我们的）文化！ I take it as " The sword can destroy our country, but can not destroy OUR culture." or: Our country(bodies) can be destroyed, but our culture(souls) will never be destroyed. If you want to say something like "Death can not destroy culture", I guess "死神摧毁不了文化" will do. The whole sentence is like: 刀剑或许可以毁灭我们的国家，但死神是无法摧毁文化的。 The sword here means physical forces, and here it's better to be translated into "刀剑" or "武力”instead of "剑".

ur sentence is ok,but that's not perfect enough. for instance,destroy means 毁灭，but in chinese,毁，灭 has a bit difference. 灭火=put out a fire 灭顶之灾= a catastrophe，it's like the catastrophe of dinosaur eg恐龙在一场灭顶之灾过后，从此灭绝。 so 灭 is Thoroughly，and 毁 is sth,especially building and hope has been destoryed so ur sentence could change to 刀剑或许可以毁掉我们的国土，但却灭不了我们的文化 ps：please pay attention to chinese word，for the melody，it‘s often arranged as one to one，two to two

just for your reference, hope u can understand since my english is just soso...in this case, the word "sword" may be considered as a kind of metaphor which means the power or violence, so if u translate it directly into 剑, it may sound werid.....it is the exact feeling i felt the frist reading this chinese sentance...武力可以推翻政权，但死亡绝对不会灭亡文化。 may be better.....

i think the second paragraph is right. But when considering the first paragraph, if you say "The sword can destroy our country, but death can not destroy culture." you mean "剑可以灭我们的国，但是这种死亡不能毁灭我们的文化。" I don't know what you actually want to express. As i see it, you want to express " the sword can destroy our country, but the death of citizens resulted from the war which aimed to destroy our country can not destroy our culture." Am I right?

“剑可以灭我们的国，但是不能灭我们的文化”it's ok