Doing what F1 does is out of the question because of cost. However, a one-off off season exhibition race (a la Japan in the mid-90's) would be interesting to see. And by international, I mean outside of North America. NASCAR should take Sprint Cup to Canada for a points race or two (Gilles Villenueve or maybe when it's built, the Fort Erie Track)
There is no reason for it not to expand if there are people who want it to. Many sports that originated in specific countries have spread across the globe to become famous and loved in other areas, such as baseball in Japan. Everyone loves racing of some kind, and this should not be confined to one country.
I'm not a NASCAR fan but racing is a sport popular in much of the world. I'm not sure if the areas that embrace rally racing would do the same for NASCAR, but if there's an indication that they would then I see no reason to not expand. It's not like a team sport where there's home field arguments to be made, individual sports should expand to where they're wanted.
People enjoy NASCAR, so why shouldn't it go international? Going international would simply open up the sport to more competitors, and get more countries involved in the spectacle. I see that as a great thing for the organization. The more people that watch the better off any sport, ever. Fans are just as important as drivers!
There are three very good reasons why international NASCAR would be a bad idea. First, the logistics of moving racecars all over the world would be cost prohibitive for the racing teams. Second, the current racetracks in the United States are only built to accommodate so many teams, and additional international teams would push many established teams out of the sport. Lastly, international NASCAR would not have a need for so many tracks in the United States, as they would need to go to several continents to race. This would cause many racetracks to be minimally used; not generating enough revenue to keep them maintained.