Question: Could you please expound on the separation of Church and State, and how it ties into other motorists yelling out of their car windows "pray at home!!" when they see the Rosary hanging from my rear view mirror?
Answer: The US Constitution does not separate Church and State, at least not in the sense of making one antagonistic to the other. "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof…."1 That means that the US cannot have an officially established State Church in the manner that the Anglican Church was established in England or the Catholic Church was in Spain at the time the Constitution was written. That this "non-establishment" was not intended to keep individual citizens and even governmental entities from enjoying the benefits of religion is clear from the second part of the clause, which guarantees the free exercise of religion. The public expression of religion is in no way prohibited by the Constitution, not even in governmental facilities and organizations. Both houses of Congress and the Supreme Court have chaplains, as do the Armed Forces where the chaplains are commissioned officers of the United States. Our priest and other clergymen from the area are called on from time to time to open the City Council meeting with a prayer.
If the "separation of Church and State" is actually greater than what is outlined in the Constitution, it is because Americans have acquiesced to the establishment of Atheism as the state religion - quite in violation of the Constitution. Freedom of religion is but one of the many guarantees that have been infringed over the years due to the apathy of our citizens. As citizens and as Christians we have a duty to be familiar with our rights and responsibilities, and to exercise our appropriate role in the process of government. (A reflective reading of the Constitution might be a good place to start -- comparing what the "Supreme Law of the Land" says with what you actually see taking place.)
It is often remarked that "freedom of speech does not give you the right to yell 'fire' in a crowded theatre. Likewise the freedom of religion cannot be exercised to the detriment of fellow citizens. You certainly have the right to hang a Rosary on your mirror - but, to exaggerate a little with the example given in the question - you have no right to drive with grapefruit sized beads blocking your vision. Nor do you have the right to drive blindly on a 65 MPH expressway at 15 or 115 because you are deep in meditation on the mysteries.
Civility in speech and behavior, as well as any laws that may have required them, have fared even worse than our Constitutional guarantees. No one has the right to express his views about religion or anything else in a violent or threatening manner. And people have a reasonable expectation of privacy; an expectation that strangers won't butt into private conversations and solicitors won't call at unreasonable hours. Of all places, the highway is the wrong place for anyone to try to convert another to his point of view!
As Christians, we believe that we have the truth, that God sent His only-begotten Son to teach us what He expects of us for salvation. Not only do we want to share the "good news" with others, but we have been commanded to "make disciples of all nations." But that doesn't mean yelling out the car window or starting bar fights. Our efforts at bringing the truth to others ought not be invasive or threatening; those strategies are likely to fail anyway. Probably the best efforts are made through good example, by letting others see how the Gospel has elevated our lives. Fraternal correction ought to be gentle, not haughty. If we intend to preach in public there are appropriate forums for doing so, from the town square to the mass media to the Internet.
And let us not forget to pray for the conversion of infidels. The man who yells about your Rosary on the Interstate is obviously in need of prayer, but so too are all those who lack the Faith. The greatest disservice done by modernist ecumenism is its theft of prayer for those who need it.