This question is inspired by the fact that Donald Trump is Republican nominee for next president. However, I am going to break rule there and here, so please assume we are talking about alternate Earth:
So, lets have country with landmass 9,6 million km2 and about 350 million citizens. This country has one of the strongest economies on the world and is in the club of eight strongest economies.
Yes, the description still fits the USA, but here what is different. The current mindset of the people.
The people of this country started to fear outside world. It feels unsafe to them and they feel that visiting people are more of threat. So they elect a new president, who has simple promise: Build the wall.
And assume this president delivers. In next 2 years he manages to build the wall around the most problematic parts ot the border. In his first 4 year term he manages to build the wall around 70 percent of the borders.
This president is re-elected and in his next 2 years he manages to build the wall all around the borders (where can be applied. So if border is made by water body the wall is not build there)
But the mindset of fearing the outside world does not end there. People of this country want to stop as much trade with outside world as possible. As the borders are being sealed more and more, the people also want to cut themselves off the outside world.
Trade stops and incentives are made to create the goods inside the land of this country. Scientists are stopping international exchange, tourist visa are stricter every next year.
Can you keep strong economy of rarher isolated country?
I would like to keep economy strong but the country isolated. But I feel this contradicts itself.
In other words: If USA starts isolating itself from outside world, will their economy crumble?
And again: I know the above model does not really fit current USA. This is why I require you to imagine alternate Earth where the above apply