Much more likely sounding/meteorological balloons - a lot of those are sent up every day, worldwide, with payloads that are roughly cylindrical in shape. And some of them can traverse huge distances, even across oceans, so such "UFO" doesn't need to originate locally at all.
A strong jet stream can exceed 250mph.
https://twitter.com/markp8183/status/1546936037112393728
EDIT: To give a more clear example. It took XL-Calibur a little more then 30 hour to travel from Hudson Bay to Yellowknife. That is not much shorter then some distance between Montana and Huron
My suspicion is that the descriptions have been of the payloads. They sound like balloon payloads. Maybe the balloon is low visibility. But doesn't explain why government doesn't mention balloons.
The outside possibility that isn't aliens is anti-gravity. I would strange that anyone who developed anti-gravity would keep secret and use it like this.
The first balloon didn’t have this consideration because it could be seen from the ground.
Your enemy only needs to be slightly better than your capabilities to beat you. If they can judge it accurately, they can more efficiently spend resources to counter your ability. If they misjudge, they either waste a ton of time and money, or they end up outmatched.
It’s like a game of poker. Those who are good at strategically releasing partial information are at an advantage.
So they call it an object because that's what they know.