If the USA would like to live just on their own and forget all other countries they will go back to the stone age.
The US exports about 1.5 trillion dollars that would not be exported anymore. So it should not be produced anymore, which means high unemployment unless the US itself would buy these 1.5 trillion dollar products. But as they don't buy it now why should they buy it then? They don't need these unnecessary products.
Same problem with 2.5 trillion imports. They import for some reason: cannot produce it themselves or the raw materials are not found in the US. So many products would not be available anymore.
You have a very simplistic way of thinking and you have no clue about the positive impact of globalism. Just like your idol Trump.
Outside the US we should then block Google, Facebook, Twitter, Microsoft, Apple, Coca Cola, Mc donalds, Boeing, ....
And the US would have this year a shortage of probably over a billion masks resulting in much more deaths as these masks had to be bought in China.