On Thursday, President Trump thanked his Russian counterpart, Vladimir Putin, for expelling hundreds of U.S. diplomats from Russia.

Trump explained, "I want to thank him because we're trying to cut down our payroll ... I'm very thankful that he let go of a large number of people because now we have a smaller payroll. There's no reason for them to go back. So I greatly appreciate the fact that we've been able to cut our payroll of the United States. We'll save a lot of money."

Whatever motivated Trump to make that statement, he was wrong to do so.

First off, it's nonsensical. After all, the U.S. diplomats formerly stationed in Russia are not losing their jobs. Instead, they are returning to Washington to await either another foreign posting or a domestic position. In addition, while there may be some limited savings by the State Department's forced firing of Russian employees, this won't amount to much money.

The average Russian makes around $6,700 annually, so even assuming 500 of the 755 number of reduced staff are Russians, and that they are paid $8,500 a year, the total one-year savings would only be $4,250,000. That might seem like a lot, but it's a grain of sand in the multitrillion dollar Sahara of the U.S. budget.

Second, Putin's expulsion order is harmful to U.S. interests. Put simply, if Russia-focused U.S. diplomats are not actually present in the country, they cannot serve effectively. Whether in promoting trade or human rights, or in providing visa services and cultural exchanges, or in foreign policy and defense cooperation, U.S. priorities will suffer as a consequence of Putin's order.

Putin has also made it harder for U.S. intelligence agencies to operate. With fewer Americans to follow, Russia's FSB intelligence service will have a greater chance of catching U.S. spies in their tradecraft. (The Russians, of course, are fantical in their approach to counterintelligence operations.)

Third, this is an insult to the men and women of the U.S. foreign service. While Trump may have made his comments in jest, he is the chief executive of the United States. Those serving the nation away from home expect to be supported by their president. This most certainly is not that.

Finally, Trump's words hurt him personally. That's because they will only fuel the perception that Russia is holding something over the U.S. president. While Putin specifically designed this expulsion to antagonize U.S. officials in Washington, Trump's jovial response is ridiculous. His silliness speaks to a troubling trend.

Thus far, Trump has shown absolutely no willingness to criticize one of America's most avowed enemies. By now, Trump will have been fully briefed on the depth and aggression of Russian intelligence operations against the Unite States. Yet he still continues to suck up to Putin. Why?

Nevertheless, there's one good thing to come out of all this. As I've noted, Congress is playing an important role in restraining Mr. Trump from giving Putin whatever it is that he wants.