Because the world is connected internationally and we trade with each other.
Sure let's go completely isolated. Bye bye any and all major tech we could get as we rely on a few Asian countries.
Oh shit well bye to damn near every technological advancement we could help with.
Welcome to the age of the internet
When you actually look at things the united states is one of the less connected countries to international trade. During trumps reign we locked down both Mexico and Canada into our economy which accounts for most of our trade. Then we cut deals with Australia, and Japan which put another chunk into our system.
The last thing were working on is the UK who are going to get a really shitty deal because they wasted everyones time and we honestly don't need them in our trade network to do just fine. Their like a cherry added on top for sentimental reasons. Once that's all locked down the us is actually quite fine as an independent trading block.
We more or less got everything we need to function with just those trading partners.