Regarding how it is in US , I am unaware. But I would not opt for an option that asks people to have an army background before they enter politics. Yes, I agree, those junta will be filled with passion for the country and they will strive for the development of our country. But then, there have been leaders who have produced remarkable results for the country without any such background.
Say, there is a very genuine chap who, after getting well settled in life wants to join politics so that he can contribute well for the country. If he is told that " You will have to join the army and get trained" to work for the people, and if that guy is so adamant that he wants to work for the people, he might just work for a small section of his local people without involving himself in any politics. A leader could be lost.
All said, I understand that we need to have a screening system. May be some thing like an IAS. Say, some thing like Indian Institute Of Political Science exam. Still there would be people who would try to break the system . But obviously, nothing can change overnight. We need to work on it. I have a feeling that a lot of anti-social activities will be driven out in the years to come. People are being more aware. If it is because of the political chaos that one feels is eating up this country that we want to resort to getting people with army background, I feel we are betting a little too much in that regard.