The first two balloons are Chinese balloons (North America/South America), most likely ‘dual-purpose’ balloons. Essentially, both civilian research and military data collection. Object 2, 3 and 4 (UFOs) are all likely civilian balloons, possibly DoD (but that would be classified). Object 4 fits the description of a heliotrope which was possibly cut from its tether, so I guess it is either launched from some institute or is hobbyist. Hobbyists float stations in the US. Object 2 and 3 in Alaska I am leaning towards exploration balloons, could also be heliotropes, but I am in the view that those balloons were used to analyse the Arctic circle, so it could be any party, including foreign, interested in exploiting the Arctic circle of which there are many such companies in Alaska, and China, and Russia, and Europe. If these balloons aren’t licensed or registered and are a risk for aviation activities then the US has a right to eliminate them when it is within their domain, whatever its purpose.
From reading on Twitter, it seems that many in the US sending balloons don’t register them with the FAA, and many of the hobbyist balloons are unlicensed for their class, in particular Class A. I do expect the US to clamp down on this now, otherwise people will go bonkers with anything they find as unknown in the sky. The last thing the USA want is for their population to think that their airspace is compromised.