Because, once the country has a secure economy, it can start trading and investing more with other places and communities. It's very refutable to say that at any one point the United States was an isolationist. But there was definitely more interaction with outside communities as the country grew.
They have a strict interperetation. They strictly follow the consitution, taking it word by word. People who have a loose interperetation often allow for more leinency.
