The law does not define the "limits of that freedom" They fought a war based on the belief that we were given "unalienable" rights from a Creator. So the idea that the constitution gives us our rights is not what was intended. The idea is that the constitution insures our God given rights from tyranny. Tyranny being defined as those who would take our God given rights from us. The rights are ours by nature; we're sovereign in this. At least according to the declaration of Independence.
You're right freedom isn't free which is why they fought a war over it.
Your rights don't come from a god. They come from men.
If they came from a god, our ancestors would have had them, and they'd be global, not regional.
After centuries of no god taking any action as mankind wallowed under the boots of kings, pharaohs, and emperors, a group of people rose up, fought and won a war to escape bondage and sat down and enumerated a set of freedoms, established courts and police forces to interpret and enforce them, modify them from time to time with amendments, and if need be, defend them by force. No god is involved. The Bible's only contribution was to inform its readers that they were bound to submit to the king as God's chosen despot.
That last fact is probably why the Declaration of Independence gives lip service to a creator being the source of their right to revolt. If your going to ask a population of Bible believing people to do that, you're going to need to justify disobeying scripture:
"Let everyone be subject to the governing authorities, for there is no authority except that which God has established. The authorities that exist have been established by God. Consequently, whoever rebels against the authority is rebelling against what God has instituted, and those who do so will bring judgment on themselves."- Romans 13:1-2
"Remind them to be submissive to rulers and authorities, to be obedient" - Titus 3:1
And yes, the law does define the limits of religious freedom, which is why we have several prominent cases in the news right now involving bakers defying that law and being found guilty of so doing. Even if the law eventually rules in the favor of those bakers - and so far it has done the opposite - it will still be the law defining the limits of religious freedom.
Perhaps you've misunderstood what church-state separation means. It's actually a misnomer. The state has complete authority over the church operating in its jurisdiction. Whatever religious freedoms the church enjoys are granted to it by the Constitution and the law, freedoms that can be expanded or contracted according to the workings of the democratic process. If the church tries to assert that it has the religious freedom to try women a witches and burn those convicted in their witch hunts, the state has the authority and power to stop them. There is no such religious freedom even if the church claims such for itself. Such an opinion would be treated as irrelevant.
And that's a good thing for the rest of us. We don't want the church and state to be separate sovereign entities. We want the state to have complete control over the limits of the church's activities, and to keep it out of the lives of those not interested in living under the values of the church. What we want is not separation of church and state, but separation of the church and ourselves. We depend on the state to protect us from the church, which is ever knocking at the doors of government trying to get in and use the state to enforce its values on every citizen. That's what it's up to now when it encourages its adherents to vote Republican in order to get Christians onto the courts including the Supreme Court to remove rights that Americans presently enjoy that offend the church.
If that's not an idea you support - and many if not most Christians don't - then you don't respect the idea of secular government - a basic and cherished American principle that people have died to establish and sustain.
This is what the church would do if it could separate itself from the authority of the state:
"The long term goal of Christians in politics should be to gain exclusive control over the franchise. Those who refuse to submit publicly to the eternal sanctions of God by submitting to his Church's public marks of the covenant-baptism and holy communion-must be denied citizenship, just as they were in ancient Israel." - Gary North
"I hope to see the day when, as in the early days of our country, we won't have any public schools. The churches will have taken them over again and Christians will be running them. What a happy day that will be." - Jerry Falwell
"Our goal must be simple. We must have a Christian nation built on God's law, on the Ten Commandments. No apologies." - Randall Terry
"Whenever the civil government forbids the practice of things that God has commanded us to do, or tells us to do things He has commanded us not to do, then we are on solid ground in disobeying the government and rebelling against it ... There will never be world peace until God's house and God's people are given their rightful place of leadership at the top of the world." - Pat Robertson
Hopefully, you agree that such people are disrespectful of the bedrock American principle of secular government, that the government is rightly empowered to prevent them from carrying out their very un-American theocratic agenda, that that is the way things should be, and that church-state separation is a misnomer for that relationship.