Obviously as several people have said, sheer fighting prowess does not an effective army make. Supply, transportation, command, control, communications, and in some cases, a technological edge in all facets of warfare are quite telling on the battlefield.
That said, the US obviously has the “best” armed forces, if by “best” you mean able to confront and defeat any other armed forces in the world. It’s not even close. The US has well equipped, well trained and well led troops with a military tradition that teaches the right lessons, as well as having the most advanced communications, control and command systems in existence. Add to that the highly developed and battle-tested supply and transport arms and a numerical superiority to most other armed forces, and you have an almost unbeatable foe.
Sure, it’s true that other countries may have better trained soldiers, but when you take the whole package into account, the US armed forces are pretty much a juggernaut that could roll over almost anyone in a stand-up fight.
Another note- I’m not at all convinced that the IDF has better-trained infantrymen than say the US or UK. After all, the vast majority is National Guard-style citizen soldiers. What they do have is a tradition of fighting and winning, and passing those lessons to the next generation, along with a very strong motivation to stay military strong and ready due to the constant Arab threat to their borders.