In the 1930s, the U.S. Army had only about 130,000 soldiers

[True Federalist (진정한 연방 주의자)]

We didn't have to worry about being invaded by land, so we depended upon the Navy to defend the country.  The thinking was that if we did get into a war, we'd have time to mobilize and build an army before we started fighting on land.  We shared with the United Kingdom the distinction of having the largest Navy at that time.

However, if one goes by troop strength, then the number for the U.S. should be 150,000 if one includes the approximately 20,000 Marines we had.

[True Federalist (진정한 연방 주의자)]

What does here army refer to? The whole armed force including ground, navy and air? Or just refers to the ground force?

Just the U.S. Army.

If it were referring to all soldiers, it would be "armed forces" or "U.S. military"

Altho at the time the air force was still part of the U.S. Army under the name United States Army Air Corps from 2 July 1926 to 20 June 1941.    In 1935, there were around 16,000 people in the Air Corps.  I'm uncertain if they were counted in the 130,000 figure, tho I think they probably were, not that it makes much difference.

[True Federalist (진정한 연방 주의자)]

Despite this fact, I saw a movie in which Laurel and Hardy became soldiers!

Was it Beau Hunks or The Flying Deuces,in which case they would have been in the French Foreign Legion?

Or perhaps Pack Up Your Troubles where they were part of the AEF fighting in the trenches of France in World War I?

There there is Bonnie Scotland where they end up in a Scottish regiment in India.

And lets not forget the 1941 film Great Guns even if it wasn't made in the 1930s.