65.8% of Americans own their home.

Taking the statement literally i think it is pretty obvious, that most people own something and usually lots of things.

For instance even if your country is in the midst of war, or a beggar on the street, you will still own the clothes you are wearing.

Many people have jobs or benefits from governments and incomes. They may well own cars, homes with various gadgets, like televisions, cookers, washing machines etc So taking the question literally most people on the planet are owners of something. Exceptions to this rule might be babies, where everything is bought for them; they are washed and dressed and they do not formally accept ownership of anything.

Taking the statement at a more complex level, for most people ownership is inaccessible to things like: the software of a computer or mobile phone. You may own the hardware and some rights to the use software but the manufacturer retains the intellectual property rights to it. So full ownership is inaccessible.

However, be aware how the statement is conventially used, the statement is most likely referring to home ownership, (as has already been pointed out by another contributor). Many people aspire to owning their own home and it's accessibility depend on a lot of factors. These tend to be outside an individuals control and can be very challenging. They include: financial, the housing market, government rules etc.

Using an a.i search, i have come up with the following statistics which i think strongly suggests most people, world wide, own their own homes. If most people own their own homes, worldwide, it disproves the opening statement.
Highest homeownership rates

Laos: 95.9% (2015)
Romania: 94.3% (as of December 2024)
Kazakhstan: 95.0% (2018)
Slovakia: 93.1% (as of December 2024)
Hungary: 91.6% (as of December 2024)
Croatia: 91.0% (as of December 2024)
Vietnam: 90% (2020)
Russia: 92.6% (as of December 2023)
Lithuania: 87.4% (as of December 2024)
Poland: 87.1% (as of December 2024)
Bulgaria: 86.0% (as of December 2024) 

Mid-range homeownership rates

Singapore: 90.8% (as of December 2024)
Norway: 78.8% (as of December 2024)
United States: 65.1% (as of March 2025)
Canada: 66.7% (as of December 2023)
Australia: 66.0% (as of December 2020)
Ireland: 69.3% (as of December 2024)
Finland: 68.1% (as of December 2024)
Sweden: 64.8% (as of December 2024)
United Kingdom: 64.5% (as of December 2023)
France: 61.2% (as of December 2024)
Netherlands: 68.8% (as of December 2024)
Japan: 55.0% (2021) 

Lowest homeownership rates

Switzerland: 42.6% (as of December 2023)
Germany: 47.2% (as of December 2024)
Austria: 54.5% (as of December 2024)
Hong Kong: 50.4% (as of December 2024)
South Korea: 56.4% (as of December 2023)
Nigeria: 25.0% (2019)
United Arab Emirates: 28% (2017)