The US should find ways to make employers less risk-averse. There are lots of ways worth exploring. For example: maybe if you fire someone in the first 6 months you are immune from wrongful termination lawsuits and don't have to pay higher unemployment insurance. A lot of resistance to firing is also caused by moral concerns -- we could fix that by making sure these fired workers are still eligible for unemployment.
This would be extra beneficial for young people, who really just need to get a foot in the door to prove themselves -- they need someone to take a risk. Well, maybe we should reduce the risk.
Most US states are at-will states, meaning they're already immune from wrongful termination, except for discriminatory reasons. No matter how long the employee has been there.
While "At-Will" in theory means that they're immune from wrongful termination, there's some major exceptions in most of those states.
See "Covenant of good faith and fair dealing" (which in some states mean you have to be fired for 'just cause') and "Implied contract exceptions".
I say these not to indicate you're wrong, mostly to make sure the entrepreneurs around here understand that even in a lot of "At-Will" states they might not be able fire completely with impunity.
w/r/t the GP as long as the rules around a trial period are set via an employee handbook or in the contract, generally in the US we're fairly free to try people out and let them go, the US is actually more liberal in this then a lot of European countries.
Your proposal sounds a lot like the risk reduction schemes implemented in France a few years ago under Sarkozy. The net result of the legislation was the creation of a micro-job economy like we see in Germany today (and a lot of street riots). Basically, employees are "hired" with an unspoken understanding that the job is essentially a temporary position, and they will be fired without severance near the end of their 6 month term. If you look into how consumer buying power among young micro-employees in Germany has decreased, the idea may seem a bit less appealing.
You'd end up seeing a lot of 5 month and 29 day employment terms for people. It'd be no effective difference than 'contract and perhaps hire later', except so many people are averse to 'contract' work for reasons (sometimes valid ones) that have little to do with the work and more to do with the culture of 'benefits'.
I don't quite know how we as a culture do it, but we need to wean ourselves off of 'employer-provided benefits'. Getting back to a more consumer-driven market vs large employer group-driven market will make our job/work situations easier for generations to come.
This would be extra beneficial for young people, who really just need to get a foot in the door to prove themselves -- they need someone to take a risk. Well, maybe we should reduce the risk.