if its a global currency how long do you think it will stay backed by gold? If its global someone is controlling it and making decisions, who are those people? By definition a global currency isn’t going to be focused on US interests.
Yet one more example of how loose his grip on reality is.
When you buy stock in Coca-Cola, you don't ask how long a share of Coca-Cola stock will be backed by the profits of the Coca-Cola Corporation. Likewise, you're not forced to buy their stock. The same considerations would apply to any issuer of a gold-backed currency.
You're assuming that people would necessarily be forced into using some hypothetical gold-backed global currency. The only reason the US government needs to force us to use the US dollar, and punish people who offer alternatives, is because there's NOTHING backing up the US dollar except a pile of IOUs held by the Fed. The same is not true of gold.