By Difference between, Underline

Yes, terminal punctuation inside the quote is American, and the rest of the world follows the logical practice of placing them outside. Anyway, the single/double quote is also, I think, an American thing - we just about NEVER use single quotes except for the quote-within-a-quote situation...

I think the only difference between to underline and to underscore is that the latter is more often used in AmE. rgds, cairn