By sharing a common currency with weaker European economies like Greece and Portugal, Germany's currency is kept much lower than it would otherwise be in a free market scenario, making its exports incredibly competitive overseas. On top of this, the nation is traditionally frugal and runs a massive trade surplus due to its weak demand for imports.
To put things another way, once money enters Germany it has a hard time leaving the country. The money is largely sequestered in German bank accounts, and this slows down the velocity of money and pace of economic growth in the Eurozone. The United Kingdom has historically had a very one-sided trading relationship with Germany, according to data from the Office for National Statistics.
Seeing how much Germany benefits from the European Union and shared currency, it is little surprise that the nation is so strongly opposed to Brexit and the prospects of other nations leaving the union. In fact, the issue of Germany's trade surplus isn't just America's problem. The economies of the U.K and Germany are deeply intertwined to Germany's benefit. And while money easily leaves the U.K to Germany, it doesn't easily come back. Brexit will most likely hurt Germany more than it hurts the United Kingdom.