The idiom is "little to no", and it applies best to non-countable nouns but possibly to countable nouns too. This is the "proximity" rule, where the closer word tends to determine agreement.

So we can say

There are a few apples left

There are no apples left

We can't say

There are little apples left (unless we mean the remaining apples are small)

But we can say

There are little to no apples left.

But it might be better to say

There may be no more apples.

Or some other rephrasing

In the particular example, the simplest way to improve the phrasing is just to use "defence" as an uncountable noun:

The problem here is that we are left with little to no cultural defence against any force which would want to conquer us.

The idiom is "little to no", and it applies best to non-countable nouns but possibly to countable nouns too. This is the "proximity" rule, where the closer word tends to determine agreement.

So we can say

There are a few apples left

There are no apples left

We can't say

There are little apples left (unless we mean the remaining apples are small)

But we can say

There are little to no apples left.

But it might be better to say

There are few if any apples left.

There may be no more apples.

Or some other rephrasing

In the particular example, the simplest way to improve the phrasing is just to use "defence" as an uncountable noun:

The problem here is that we are left with little to no cultural defence against any force which would want to conquer us.