The U.S.A needs to build mech warriors.(These things: http://www.unknownak.20m.com/images/madcat.jpg)
Practical uses:
Scaring other nations who wish to attack, who wants to mess with a country with 20ft robots with lasers and machine guns?
Military use, (Obvious) With lasers and the ability to walk up to tanks and crush them in one step.
Ability to tack tough terrain, were as tanks and other military vehicles can get stuck or slowed in marshes and bumpy terrain a mech can just stroll through it.
Notes:
Make them out of strong but light weight matieral.
Must be awesome looking.
Can use either drones or pilots.
Conclusion; please take this idea into consideration.