"Is the value of "billion" exactly the same in the United States ofAmerica as in Great Britain?"
"These days, in most contexts, yes."
But using "billion" might cause potential misunderstandings. I would recommend using "thousand million" or "milliard" for ten to the 9th power. Numbers like "billion" and "trillion" for larger quantities are better avoided at all, which is no so difficult because such huge numbers are rather meaningless to most people.
Gerard van Wilgen -- www.majstro.com (On-line translation dictionary / Enreta tradukvortaro) www.travlang.com/Ergane (Free translation dictionary for Windows / Senpaga tradukvortaro por Windows)