Is it beneficial to the U.S.
Not for people who want the U.S. to stay a sovereign nation.
Your question shouldn't be, "Is it beneficial to the U.S." Your question should be, "Is it beneficial to Americans", or "Is it beneficial for me."
The U.S.A. is a sovereign nation; so it might seem that a one-world government would be bad for it.
Two hundred twenty-five years ago, the thirteen American colonies became thirteen sovereign states, under the Articles of Confederation. They soon decided to relinquish parts of their sovereignty, and united under the U.S. Constitution.
Seventy years later, eleven states regretted that decision to the point where they seceded from that union, and again became a Confederacy. One of the end results was enactment of the fourteenth amendment to the Constitution, which defined U.S. Citizenship as something apart from state citizenship, thus making the U.S.A. truly one nation, and diluting the notion of statehood.
In 1992, several European nations formed the European Union, and today there are 27 member states. The European Union could be considered a prototype for a future World Union. A analysis of the effects of one world government could start by examining the European Union. You can question whether or not states and individuals are benefiting from the Union or not.
One big difference between the U.S. Constitution and the European Union is that, whereas the U.S. Constitution derives it power from a two-thirds majority of the states, the European Union derives its power from unanimous agreements. That's the reason they have no Constitution yet. The first Constitution failed to get unanimous ratification, and the reform constitution was rejected by Ireland last June after being ratified by 25 of the 27 states.
Note that at the very time that the European Union was being formed, President Clinton was trying to appoint Lani Guinier to the cabinet post of Attorney General. She was rejected, mainly because of her stance on majority rule.