This uses a combination of techniques - taking 'leaders' (first letters) and connecting to American slang for a small amount of money.
Look at 'These world leaders' as instruction to take first letters. The repeated 'It's … it's' gives you the letters to work with. The Roman numeral connection leads to the first word, and American slang for a small monetary amount gives the second word.
Answer: TWO BITS | 'These world leaders' means take the first letters of 'It's … it's' = I, I = II in Roman numerals = TWO. 'Worth little in America' = BITS (slang for 25 cents, a small amount).