From Wiki
In December 1948 the Secretary of State authorized the US Consul in Amman to advise King Abdullah and the officials of Transjordan that the US accepted the principles contained in the resolutions of the Jericho Conference, and that the US viewed incorporation with Transjordan as the logical disposition of Arab Palestine.[5]
The United States subsequently extended de jure recognition to the Government of Transjordan and the Government of Israel on the same day, 31 January 1949.[6]
The 1950 State Department Country Report on Jordan said that King Abdullah had taken successive steps to incorporate the area of Central Palestine into Jordan and described the Jordanian Parliament resolution concerning the union of Central Palestine with Jordan.
The report said the US had privately advised the British and French Foreign Ministers that it had approved the action, and that "it represented a logical development of the situation which took place as a result of a free expression of the will of the people."[7]
Perhaps you should read more than just Arabist and third worldist propaganda. Three countries recognized the Jordanian Annexation: Iraq, Pakistan, and the United Kingdom. Despite our State Department being owned by the oil lobby, the US wasn't once of these.
But having accepted Jordan's invasion in 1948 and subsequent annexation as proper, you have no leg on to oppose Israel conquest of this land in a defensive war started by Jordan. Jordan attacked Israel in 1967.