The whole theory of the "Separation of Church and State" is nowhere in the Constitution. The first amendment says that Congress will not establish a national religion, but not use religious principles in governing, which can actually make everybody more moral. Now, this myth is used by the ACLU to target people who want to express their religion. How does this make any sense? God is everywhere, and the idea that it can be separated from anywhere is a myth.
If you listen to most, especially conservative, politicians, they speak a lot of religious or religion-influenced rhetoric. When making laws, such as banning gay marriage, abortion, stem cell research, among others, they appeal to their religion, rather than science. I have heard politicians publicly state that the United States is a Christian nation. How can church and state be considered separate if politicians are claiming that the entire nation is Christian? I understand that we all have the right to religious freedom, and that's fine, but it should not influence how our country is run. When faced with difficult political decisions, personal agendas and religious affiliation shouldn't be what guides those in power. It should be for the betterment of our species and environment. After all, morality doesn't come from scripture, but from sympathy, empathy and the desire for our species to advance with causing the least amount of harm to all sentient beings and the environment.
Look at the stances many politicians, especially those who are conservative, take and tell me Church and state are separate. The only place Church isn't allowed right now is in public schools. When I hear conservative politicians speaking out against gay marriage, abortion, stem cell research, and similar things, can you honestly tell me that it isn't due to their religious beliefs? I do not elect officials to act on their religious beliefs, but for the good of all citizens. Being guided by religion when making political choices is not a separation of Church and state.
The rule of law based on secular and not sectarian considerations was in the forefront of the framers mindset. One need only look to colonial governments that discriminated against Presbyterian and Episcopalian churches in favor of the ruling Anglican majority by diverting tax money for Anglican support to the exclusion of others. The phrase "pass no law respecting the establishment of religion" has been interpreted by Lemon v Kurtzmann to understand that any spending or law passed by any government (via 14th amendment) must promote a secular need and must not objectively benefit one religious theory over another. The only way spending tax dollars for any sectarian purpose can be permitted is if those who don't agree can opt out of paying their taxes.
The Constitution makes no reference to any specific religion and called for keeping religion from being a determining factor in placing and/or electing an official in to office. So technically there is to be a clear line between church and state. However, one cannot deny there are ample references to God in regards to things and/or activities commonly seen as governmental. For instance, on the US dollar one can find “In God We Trust”, the pledge of allegiance has the line, “One nation under God”, and when one testifies in a court in the US, they are made to swear on a bible. So it would seem to be that the line between church and state does in fact exist, but it is a curvy one.
You can pull up laws made for religious reasons, and you can point out lawmakers and political parties doing things for religious reasons. However, it is first important to note that separation of Church and State is not meant to keep people with religious convictions out of politics, or even keep them from being guided by their understanding of religion. That would simply be restriction in the other direction. The point is for laws and government not to proscribe a religion and discard others. Now, we have had some mistakes on this front, and the United States is definitely heavily influenced by Christianity, but I don't think this makes separation of Church and State a myth. It's just not quite as well enforced as it might be.