What are the advantages of stopping all trade outside the USA?

There are no advantages.

We only represent 3% of the entire world.

We can't live just among ourselves.

The US economy would crash. The US will be in enough trouble now that China are launching the petro-yuan.

But did you think of the disadvantages?

There are none because doing that would kill the US economy. You apparently don't understand that very many US companies depend heavily on sales to other countries.

The advantage would be to negotiate a better deal with other countries. Think of it as going on strike. Here's an example for you, when people who work for a company go on strike, it's for negotiation to get a better deal.

None exist.

There aren't any.

America thrives when the rest of the world thrives, stupid people will be the end of of this country