Besides the fact that Jordan and Iraq are neighbors, and do a lot of business, there are perhaps historical reasons for doing so: the last Iraqi King, Faisal II, (murdered at age 23 in 1958, along with his entire family, by some of Saddam's equally unsavory predecessors), was a cousin of his fellow member of the Al-Hashimi dynasty -- King Abdullah II.
Dynastic and commercial reasons aside, I wonder why the Jordanians are doing this ? Mind you, this is good as far at the United States is concerned, but the Iraqi government is not what one would call stable, and King Abdullah II, already a poor risk for a life insurance policy, will possibly make himself a few more enemies this way. Also, God protect the ambassador and his family, because the bad guys will certainly be after them.
There are a couple of possibilities: First, if Iraq breaks-up into its constituent Sunni, Shiite and Kurdish parts, the Sunni area of the country, that bordering Jordan -- is not especially viable, given that, unlike Kurds and Shiites, Sunni Iraq has no oil (at least that it doesn't have to fight for), and lacks access to the sea. Jordan, a Sunni state also, doesn't have much oil -- but has the port of Aqaba. Rolling up Sunni Iraq into Jordan actually makes a bit of sense, and might help King Abdullah's country with another big problem by diluting the political power of his Palestinian residents, who are somewhat unenthusiastic subjects of his House. It would be interesting to know what the new ambassador's instructions might be about contact with Sunni leaders.
Less fancifully and more immediately, I suspect the United States is leaning on its friends (a kinder term than clients), such as Jordan, to show their loyalty, following Hezbollah's recent triumph in Lebanon. Moreover, King Abdullah probably in any case now feels a certain draft; a cold wind blowing from his family's old enemy Syria to the north, and is looking to reassure the United States of his regime's value.