The US has about 250 billion square feet of residential floor space, spread across about 100 million individual buildings:
The majority of that square footage is found in single family homes, which make up a bit over 75% of residential square footage. Multifamily buildings (duplexes, apartments, condos, etc.) make up another ~18% of the square footage, and the balance goes to mobile and manufactured homes. Within multifamily, we see the majority of square footage is in smaller buildings — 2 to 4 unit buildings, or buildings 3 stories or less. Multifamily buildings taller than 3 stories make up just over 3% of US housing by floor area — your mental model of “typical apartment building” should be a garden apartment rather than an urban high-rise (the US actually has more square footage in mobile homes than it does in multifamily buildings taller than 3 stories). Over 90% of housing space in the US consists of single family homes and low-rise apartment buildings.
This affects energy use:
Modern housing uses substantially less energy than older housing on a per-square-foot basis. A 50-year difference in house age translates to roughly a 50% reduction in energy use. Most of that reduction comes from reduced energy used for heating.
After age, the largest variable that affects home energy use is climate — homes in cold climates use about 30-40% more energy than homes in warm climates, most of which is due to increased heating requirements.
Other than mobile homes, we don’t see a huge amount of variation in energy intensity between different types of housing (single family, multifamily, etc.) On a square-foot basis, single family homes actually use less energy than multifamily housing. Differences in energy use come from the fact that single family homes are much larger than multifamily housing.
Likewise, differences in energy use between the US and European houses stem from the fact that US homes are much larger than European ones.
We don’t seem to find much difference in energy use from across similar homes in states with different level of energy code strictness, though the data here is limited.