I think the larger the marketplace the better, with a global market place the US can import goods at a low price and they can export their goods to the highest bidder, the larger the market the more options you get in this regard, so overall I believe everyone benefits from global trade.
It is good for the USA due to the fact that we have various resources and have more than we can use and trade is good for not only the country but also the citizens. The bad part is that companies outsource their labor for cheaper. It would be better if we could increase the price of our dollar so that we could be stronger in the market place.
A global marketplace is good for the United States, especially if we are doing the vast majority of the exporting. And it's good for imports too, because that builds friendlier relationships with other countries, which is becoming vastly important in the modern world as it is shrinking very quickly indeed.
The US economy has already been hurt by NAFTA and CAFTA. We have lost many manufacturing jobs - many in places that depended on them. Many places can make things a lot cheaper than us, or in some cases better, such as electronics in Japan. While some good can come from a global market the US is hurt in terms of providing jobs.
Overall I would say the global marketplace is not inherently good for the United States, but it is worth while. America is, or rather was the land of plenty, for a while. We enjoyed it but it's not sustainable. I believe the global marketplace has allowed wealth to be spread a little wider, which in turn means some bad situations are improving. However, in places like the United States where things were much better, they are now getting slightly worse due to this shift. Overall I think it's a balancing mechanism. It's not all bad, but it's not all good either.