ARGENTINA ES NORTEÑO

>Not understanding what the N means in NATO.

It's a moot point anyway for a couple of reasons.

NATO mutual defence obligations only apply north of the Tropic of Cancer. The same reason the alliance didn't intervene in the Falklands War back in '82.

If Milei wants close cooperations with NATO, that's already possible. Australia, Japan, Colombia, and even Mongolia are doing this now.

Also, there isn't a snowball's chance in Heck that Britain would let Argentina join while it maintains an active (but toothless) claim on UK territory.