Do you remember how 米国 can mean "America?" That 米 means America sometimes. So, when you see all rice (I mean, America), you can think of this word as meaning All America (sort of like how 全日本 means "All Japan.").
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
number one in America
all-American hit chart
the US Open (tennis)
This is a popular movie in all of America.
What is the number one song on the US hit chart now?
An interview offer came from a nationwide television station.