In the 1920s, Ford's Model T brought about massive change. It popularized the automobile, and soon, they were everywhere.
Ford pioneered mass production techniques in the automobile industry, allowing him to produce millions of cars for little money. This in turn led to the widespread growth of car ownership, weakening the railroad industry. It also caused suburbs to expand, and workers to become commuters, shaping the car centered world we know today.
The introduction of cars was also very important because it became a symbol of freedom and independence, allowing people to "work to live", rather than "live to work". It also greatly improved standards of living for the well off, creating a consumer society that is now synonymous with America.
The refinement of the airplane by the Wright brothers allowed it to be used more practically, and thus it became one of the most influential inventions of the 1920s.
While the airplane was at first extremely dangerous and unreliable, as inventors improved on it, the airplane became a feasible vessel for transporting cargo, mainly mail. This in turn dramatically shortened mail transport times, better connecting the US and shaping the air freight system of today.
The airplane gained fame with Charles Lindbergh's record breaking flight over the Atlantic Ocean, and the airplane would later become a way for people to travel across the entire United States in less than a day. This helped to bring the country closer together, and eliminated the days of having to travel days or even months from coast to coast.