How could the German recession create problems for the United States?

A German recession is having a weak direct effect (via foreign trade) on the United States. But it may have a very negative indirect effect on the United States via the following mechanism: The German recession leads to a more expansionary fiscal policy in Germany and in the rest of the euro zone; This eliminates the euro zone's external surplus; However, this surplus was to a large extent lent to the US Treasury, as since 2013-2014 the euro zone has replaced China as the main lender to the United States; the disappearance of the euro zone’s surplus would therefore lead to a major problem in financing the US external and fiscal deficit s .