Cutting off trade with all parts of the world means that America will be independent and a World power that doesn't depend on the trade of resources and goods with other countries.
While trade has its benefits- if a country cuts off trade there can also be some seemingly benefits.
This has been an issue in the news as of late. America is seeking to create and sustain our own products and business, limit immigration so Americans in need of jobs will be more able to locate them with less competition, etc.
It could mean many things but the most common explanation is to own up to your mistakes. to not walk around looking for someone else to blame. It depends on how it's used in context though.
