As long as you have a picatinny rail on the rifle it will work and be easy to mount. However it is an AR height optic so it may not be ideal on the Ruger American, as you will need to adjust your cheek weld to use it.
You would need to put a picatinny rail adapter on first, then you could mount any optic you like. The few extra dollars you would have to spend on a rail adapter is nothing compared to how much any other optic with this many features would cost. Plus for about $30 you can get a screw on 2x magnifier or if you need more there is a 5x magnifier available. I own an EOTech, AimPoint and a Sig Sauer along with this same Gen3 L-HD7 by Lucid. For this sight with the 2x & 5x magnifier still cost me less than any of my other sights without a magnifier let alone 2 and has the 2nd best reticle options but it didn't cost $1000 like my Sig did. The biggest downsides to this sight 1 it's not made in the USA and 2 only applies to Military & Law Enforcement operators and hog hunters, it's lack of Night Vision capabilities.