From a Buzzfeed list of tweets about Home Alone, here is one that considers the primary setting for the movie:
While the house may appear to be a McMansion because of its size and suburban settings, there are multiple pieces of evidence to counter this (compiled from multiple websites including fancypantshomes.com, themirror.co.uk, and census.gov:
1. The home was constructed in 1920. This construction predates McMansions by roughly six decades.
2. The home sold in 2012 for just over $1.5 million. This is beyond the price of most McMansions.
3. The home does not suffer from the architectural issues facing many McMansions (likely because it was built in 1920): it has a consistent brick facade, a symmetrical front, and not too many gables.
4. The home is not in a suburb with residents striving to look wealthy; this is a wealthy suburb with a median household income of $220,000 for its over 12,000 residents.
5. Because this is an older and smaller suburb, it is indeed possible to walk from the McCallister house to downtown which is less than half a mile away. It is possible to have big houses located in walkable neighborhoods (which is part of the appeal for some teardowns in older suburban neighborhoods).
Kevin McCallister lives in a big house, a house for wealthy people, but it is not a McMansion. The primary setting for Home Alone is a large and older single-family home far beyond the reach of most Americans and located within a walkable and wealthy suburb.