That's an impressive sounding justification for a belief in something that does not happen.
What the argument overlooks is the fact that foreigners do not buy American goods with foreign currency. They sell their things to get dollars that are used to buy our exports. That 'shift downward to the right' on one graph is canceled by an opposite 'shift upward to the left' on the other.
No, they exchange their currency to get our currency. And with a weaker dollar, their currency buys a lot more US dollars.
Let's say we want to purchase Audis made in Germany. We would have to purchase Euros with US dollars in order to have the correct currency to purchase them. And in order for Germans to purchase Boeing Aircraft, they would have to purchase US dollars with their Euros in order to have the correct currency to purchase them.
When the dollar weakens, Europeans are able to purchase more dollars for their Euros, thus making the price of American goods less expensive in terms of their Euros. At the same time, it requires more dollars to purchase Euros, thus the price of European goods relative to the dollar goes up.
Your mistake is that you are assuming a zero-sum game in the short run. That is not the case. The fact that we even have a trade deficit quickly dispels that notion. When we run a trade deficit with Germany, dollar flow out of the US and Euros flow into Germany. And currency exchangers do a brisk business selling Euros and buying dollars.