And the other aspect of this is that a lot of americans own guns. Part of the reason the Knock rule existed is that it was better to warn the homeowner than let them think it was a break-in. (Particularly as the houses these police are likely to enter are more likely to have guns in them...)

Then end result being, in addition to an erosion of rights, probably an uptick in shootouts and cops getting killed. Which will be especially great if the cops get the wrong address.