1. Manpower - Israel has a huge pool of very talented young men and women who already received very good training in the army and the security services. It also budgets paying them well. Make no mistake, airport security in Israel is no McJob, it is a prestigious, well-paid position, manned by the top classes of society. America is relying on cheap, unskilled labour for these jobs, and transitioning to an Israeli employment profile will bankrupt the system.
2. Volume - Israel has only one major international airport (and even that one is quite small). As far as airport security is concerned, it is a very local problem which can benefit from focused attention. The US has to protect hundreds of very busy airports, and they all have their unique weaknesses.