What he said. Isolationist is a type of foreign policy. Capitalist is a type of economic policy. The only thing "Isolationistic Capitalism" brings to mind is that time when Thomas Jefferson closed off the American Economy to Europe.
We didn't do so well, lol!
I'll answer both questions though, if you'll let me.
1. In terms of foreign policy, no, I do not think we should be isolationists. It might've worked in 1800, but we weren't a world power then. We are now. One of two superpowers. To the majority of the world, we are the ONLY superpower. What we say goes. And, though overstated and quite cheesy, "With great power comes great responsibility". We need to set an example. Everybody looks to us. Yeah, they criticize us when we mess up, but they still need us. We need to be the leaders, the role models. How can we possibly expect any other country to act respectably if we are unwilling to do it ourselves? We can't shrug off the entire world. We depend on THEM as much as they depend on US.
As for capitalism, yeah, supply and demand seems to be the best way to make things work. However, pure capitalism, as proven in the past, is bogus. Regulation is important. Not full fledged socialism, but making sure that business play fair, that the meat isn't poisoned, etc is important.