I don't follow this at all, but I'm willing to listen? How does private property require any more force to uphold compared to any other possible system? Even anarchy, if you want it to stay anarchy requires force if you have defectors.
Property (and we're mostly talking in the context of "real" property - i.e. land and maybe structures/improvements - since that's what's typically most scarce/valuable in a society given the fixed supply, though some resources like water might be subject to similar discussions for similar reasons) has two states: "owned" and "not owned". Asserting ownership inherently requires force. Not asserting ownership requires no force at all.
Typically, in an implementation of absolute anarchy, there would be no ownership of property beyond, at most, two categories:
1. Property which you individually (plus perhaps your family) are actively occupying/improving/using and can prevent use by others
2. Property which you and other people interested in occupying/improving/using that property (a.k.a. a "community") can cooperatively do so
Category #1 is a difficult proposition in a stateless society, since it definitionally means that your occupation is at the exclusion of a broader community. All but the absolute smallest of "communities" (if you could call them that) would likely outnumber you. You could probably recruit other community members to your cause, but - definitionally speaking - if you're able to get enough people on your side to avoid being outnumbered, then congrats, your property is probably in Category #2 and collectively-used.
You're right that private property and community property require an equal amount of force to uphold, but the thing is that per person community property requires less force per occupant. Thus, unless you've got a force multiplier that's unavailable to the broader community, you're gonna have a pretty hard time asserting "private" ownership of anything that the broader community claims to "own".
From a purely anarchistic point of view, European settlers were within their rights to settle upon and use that unowned land. They weren't, however, within their rights to to use that "unowned" land at the expense of other people already using that land, and thus the Native Americans were within their rights to defend against such a deprivation of access. Unfortunately, the Europeans had numbers, guns, and smallpox on their side, and as the Native Americans retreated further West the Europeans continued to spread.
And to be clear: the Native Americans were using that land. A reasonably-healthy wilderness ecosystem is crucial for hunting, as any hunter can attest even in the modern-day; kinda hard to hunt bison if there ain't any bison.
If there is no concept of private property, the need to defend ownership ceases. If no one owns anything, there can be no claims - and counter claims. Like a happy family where your brother's meal is also yours, and vice versa - depending on how hungry you are.
For the record, I don't support the latter stance and believe Marxism is catastrophically ignorant of innate human tendencies. But as an ideology, it is worth exploring to reexamine our own relationship with and understanding of private property.