This is not true, and is based on the false zero sum game fallacy. The assumption behind it is that value is fixed, so that if someone gains more of it, someone else will obtain less. People commonly ask who gets the best of a bargain, wrongly assuming that one party gains at the expense of the other. In fact, value is not a fixed property of objects, but something in the mind of those who think about them. People are different and they value things differently; and value is not fixed or in limited supply. When a voluntary exchange takes place it is because each party puts greater value on what the other party has than they put upon what they are ready to trade for it. When the trade takes place, each party acquires something they value more than what they already had. Both gain in value; this is how wealth is created.
It is not a case of one party winning and the other losing. Rather is it a win-win situation in which both parties have added value to their lives.
Just as both usually gain in a voluntary bargain between people, so do both sides usually gain in a freely-entered exchange between nations. People in one country trade what they have in return for what they value more from the other country. Both become wealthier as a result. It is trade and exchange that makes countries wealthier, not trying to accumulate precious metals or plundering wealth from others. When countries abandoned the idea that they could grow rich at the expense of others, the world's wealth began to grow dramatically. Trade has made everyone winners.