Learn English – Should I use a hyphen with a phrase involving “then”

Whether or not prefixes are hyphenated depends a lot on which prefix it is. In general, newly coined prefixes or neologisms are likely to take a hyphen, while established vocabulary tends to lose the hyphen. There are no absolute rules, though.

That being said:

• autopopulate is probably wrong, since the use of the prefix auto- in this sense is very recent.
• auto populate is also wrong, since verbal compounds are never written separately
• auto-populate is probably the preferred answer

The Chicago Manual prefers a spare hyphenation style; their guideline is "hyphenate only if doing so will aid readability". So Chicago would recommend North America based.

When I look up based in Wordnik, all of their examples where based is preceded by a proper name use the hyphen, e.g., U.S.-based, N.Y.-based, and so North America-based by extension.

However, I would share your reservations about joining America to based, and would use North America based.

The Chicago Manual notes:

Far and away the most common spelling questions for writers and editors concern compound terms—whether to spell as two words, hyphenate, or close up as a single word.

To aid your decision, they offer this handy table.