What are some technologies that the U.S. is using or can use to build a real life equivalent of an Iron Man suit? How is technology progressing and how will this unfold?

Structurally, the starting place is as Prateek Mishra mentioned, a robotic exoskeleton.  This is the state of the art today: The biggest obstacle is that there is no Arc Reactor. How to power all the electric loads without making TALOS into a heavy and bulky thing?  Battery technology isn't up to the job within the specified envelope. Wearable solar panels are not going to generate 1Kw per hour unless they add a 50 square foot cape to it-- then it'll be more Batman than Iron Man. At least his cell phone will stay charged. Thermoelectrics and kinetic energy harvesting technology are still at a very early stage.  There is no Mr. Fusion. Maybe they'll need a robotic camel to carry all the juice the warfighter will need? Given the limits on the sources, the other places to look for solutions are extremely energy efficient electronics and motors. For some reason the Army has always wanted to have thermal management technology, too, such as Peltier devices.  This is likely not going to happen anytime soon.  They are inefficient, add bulk and performance is highly limited by the environmental temperature.  They'd save a lot of trouble if they designed a model for hot climates and another for cold.  The Peltier is also another energy sucker.  Maybe they should just drop that idea or go for a passive solution. How about a whole suit full of this just so you can keep cool?  The Army also wants wearable armor that provides a presently impossible degree of protection.   The smart fabric sensors and conformal antennas are already good to go. Today's displays are up to the job, too.  You can see a lot of what's needed here:

Sure, we could build an "Iron Man"-like suit.  Standing in our way is one area where we can't seem to substantially advance in.  Ready for it? Batteries. If we figured out how to store massive amounts of energy in a device that fits in your hand, safe as a AA, and maintenance free  (Tony Stark's "chestpiece" - the arc reactor) - then no doubt an "Iron Man" like suit would exist.   If we had Stark's "battery" today, possibilities are endless.  Super strength (aka power steering for  your joints) could be achieved with a new generation of actuator that takes advantage of all that energy to remain small, agile, and super strong.  Ion plasma drives, high power lasers, electrothermal, etc. could all be used for propulsion and weapons. On the bright side - if such a battery could/did exist - it would most definitely wreak serious havoc on our society. -Andrew Except where Tony Stark seems to defy the laws of physics on several occasions. i.e. when he his the ground after falling out of the sky - nothing can save you from the forces acting on your body resulting from going triple digit speeds to 0 within a a few microseconds.  Your body would be atomized.).

This question has been asked in several forms by several people.  See the answers posted in for the practical science limitations to building an 'Iron Man' Suit. Short Answer is that we can build a suit of hi tech armor, we have made good progress on exo-frames which increase operator's strength. The suits don't fly.  The exo-frames reduce mobility even as they increase strength, are bulky, and have severe power issues.