This will soon be the case for me - can you explain how that works? Do I just bring my old and new passports to the border and show them both?
>A US B1/B2 Visitor Visa will generally get you into an additional dozen or so countries
It can work the other way too. Due to a mix up with dates I had to get one cancelled (and a new one issued) so the original in my passport has a huge red "Cancelled without prejudice" stamp across it. The border guard at Honduras was not happy - he figured if I wasn't allowed into the USA he didn't want me in his country. It took many, many hours to explain I had another perfectly valid USA visa.