Actually, in the U.S., you literally have that specific constitutional right.
The First Amendment protects "spouting off in the public square without consequence" via the Freedoms of Assembly (the right to gather), Speech (say what you like without consequence), Religion (believe what you like), and the right to petition the government.
Loud complaining or even vague and non-specific threats (such as "I'll make you pay for this!") are actually protected by the First Amendment.
There are very rare and limited exceptions, such as "directed to inciting or producing imminent lawless action and is likely to incite or produce such action".
It seems like the OP might have been conflating free speech with admissions of guilt for other crimes, but "spouting off" is not, and must never be, a crime.
like I can say what I want, but if I say "I DID CRIMES" then guess what.. that could be used as evidence that I DID CRIMES
By my reading, it wasn’t OP who did this conflating.
"spouting off..used against you in a court of law"
But, even if the OP didn't intend for these two to be tied together in this way, then a very strong constitutional right still exists for spouting off, so whether conflation occurred or not is moot.
“Spouting off” is an idiom that can also mean “speaking without a filter” and that’s what OP meant in this case.