Europeans are flouting the trading clout they have. They, for example, don’t want to reduce their 10 percent import tax on U.S. automobiles to the 2 percent the U.S. charges on EU-originating motor vehicles.

Put very briefly, Trump is wasting time trying to change the existing trans-Atlantic trading regime. He should simply tell the German EU bosses that he wants balanced trade accounts — immediately. Let the Germans figure out how to do that.

Incidentally, Trump should do the same thing with China. Let China decide how to balance its U.S. trade. And the U.S. should get out of the business of Chinese structural reforms.

None of this means that Washington should tear down the G-20 (the world’s main economic forum), the World Trade Organization or the International Monetary Fund. But it does mean that the U.S. should strongly and effectively defend its interests on all those global platforms — instead of complaining because it failed, or never even tried, to do so.

On political and security issues, the U.S. has to start out by deciding what it wants to do with China and Russia.

Here is an example: Trump is telling the Germans that they give billions of dollars to Russians for energy imports while expecting the U.S. to spend billions of dollars to defend them from Russia.

What that means is that the U.S. (with Germany and the EU) has to decide what kind of security architecture it wants with Europe’s largest country. Russia accounts for roughly 37 percent of Europe’s landmass, and that area is home to about 75 percent of the Russian population.

Quarreling with Europeans about their defense spending is also a useless exercise.

Most European countries don’t even know who the enemy is. Those in the south are concerned about terrorist attacks and huge inflows of migrants and refugees from Africa and the Middle East. Those in the north say they fear a Russian invasion — a fear their friends in the south call pure paranoia and a centuries-old hatred of Russia.

Italy, for example, announced during the NATO summit last Thursday that it won’t increase its defense spending from the current 1 percent of GDP, while its president and interior minister were fighting about what to do with a boat carrying hundreds of African migrants toward Italian ports.

Similarly, on the same day, the Czech prime minister said he would not compromise his budget balance with higher military spending, adding, with a tinge of sarcasm, that the U.S. was pushing arms sales on Europe to narrow the trade gap.