The American constitution is very libertarian just no one respects it.
For example 2a gives the citizens the right to bear arms. However thats infringed on every day in america. 6a gives the right to a speedy trial to prevent innocent people being locked up with no trial. Yet that happens all the time in the USA
4a protects against unreasonable search and seizures to be supported by oath and with a description. Yet in America a random stranger on the internet can get your house broken into by militarized police with no oath or accountability. Heck not even a simple knock first.
If we just respected the bill of rights and the constitution we would be libertarian. But now we have the kind of government that goes against our libertarian laws written into the constitution!
How do we fix that?
Article from r/Libertarian: For a Free Society