Trump has officially nominated Woody Johnson to be United States Ambassador to the United Kingdom.

Johnson owns the New York Jets and is an heir to the Johnson & Johnson company. He also raised a lot of money for Trump during the 2016 campaign.

But while it's true that the NFL is popular in Britain, Johnson is not the right pick for this job.

After all, the U.S. ambassador has a serious and demanding job. Johnson seems to be a good man, but being friends with the president is not sufficient qualification.

This was recently evidenced by the U.S. Chargé d'Affaires in London.

Rightly concerned at the public animosity fostered by Trump's criticism of London's mayor, the top diplomat responded with a public affirmation of support for the mayor. He was right to do so. Diplomacy rests on positive perceptions. Absent that, it becomes much harder for a foreign government to support the U.S. on controversial issues. Had the chargé not praised the mayor, the British government would have been very angry. They know that to support Trump, they must be able to justify that support to a skeptical public.

And that speaks to something.

An ambassador is not simply the representative of their nation. They are its face. That requires a character well-suited to the culture of the nation in question. In the case of U.S. ambassadors to Britain, that means someone who is attuned to British idiosyncracies, savvy to the U.K.'s notoriously aggressive media, and comfortable with diplomatic formality.

I'm not convinced Johnson is prepared on these concerns. While there will be some recognition that this is an opportunity to build the NFL's presence in London, Johnson's appointment will be controversial. Allegations that he engaged in tax avoidance schemes will be especially controversial. That's because tax avoidance is a particularly sensitive political topic in the U.K., far more so than in the United States.

Regardless, there's a broader point at stake here. As I've explained, it's sad that we, of all nations, send rich donors to fill critical diplomatic posts. We are supposed to be the great meritocracy. Instead, we act like a tinpot dictatorship, sending favored friends to live it up in the capitals of our closest allies.

Trump pledged to end the era of cronyism and special interests. This appointment proves the contrary.