Sure, they can collect whatever dots exist in the public domain. When they force a private entity to turn over their property (i.e., data collected in the course of business) they need a 4th amendment warrant.
But the dot collecting has to be on an individual basis, and in most cases per prior approval of a court must be had.
Or would you support the British just saying “Let’s collect all the dots in this huge city...forget going door to door...”
Are you advocating for blanket sweeps? And this has occured with friendly heads of state all over the globe.