The US Army is investigating after a helicopter was filmed performing a low-altitude manoeuvre outside the home of musician Kid Rock while he saluted.The singer posted a video of the Apache attack helicopter hovering above his Nashville home while he saluted."This is a level of respect that s— for brains Governor of California will never know," he captioned the video on Instagram.READ MORE: Donald Trump to put his name on all US paper moneyKid Rock in the Oval Office with