I've thought a lot about what might eventually drive a significant number of Americans into Bitcoin and 'ease of use + security' will grease the way, but I think more likely it will be the accelerating reality of inflation and zero/negative interest rates on their savings and pensions that will drive people to Bitcoin in spite of the lack of ease-of-use.
Bitcoin security is just a computer science problem to solve, and engineers live for that sort of thing. My first PC the TRS-80 was friggin' primitive compared to my new Galaxy Note 7 and in 10 years I suspect cryptocurrency use will be quite easy and secure.
In short , Bitcoin offers a way to preserve wealth and interact in an increasingly online world, and don't forget, for the first time, we have a viable way to opt-out into a less corrupted system.