An accepted translation of "How can more wars give us security" is "Hur kan fler krig ge oss säkerhet?" I'm reading "fler" as singular: "more war." The sentiment is the same, but isn't that a different sentence?
"More war" would be said "mer krig", considering war uncountable.
"Fler krig" means "more wars", remember that krig is an ett-ord, so in this sentence it is indeed plural, and after fler comes plural.
If it was an en-ord you would say for instance "fler köttbullar"