No, but the US had greater prosperity because of an unfortunate event that reduced the prosperity of other nations and which afforded a particular set of unique economic opportunities. It's very easy for your average schmuck to get a bigger piece of the pie when the pie is simply bigger for a little while.

Also, those jobs were always going to be exported as soon as it became economically viable to do so. That decision as never not going to be made. If you want to address the root cause of American economic inequality or job loss, you can point to capitalism's need for constant growth as the root cause. But don't ignore the historical realities of America's post-war boom economy in order to fantasize it as some mythical "lost economic golden age."

You're right that it isn't a 0-sum game, but people in power in the US have always treated it as one.