Consider the complexity of everything the US offers; from the sun splashed beaches of the Pacific or Atlantic Ocean with crystal clear waters, to the soaring Rocky Mountain Range ,encounter all of this while being immersed in a sea of multiculturalism when choosing the US as your destination to improve your English language skills.

this 指“单数可数名词” 或 “不可数名词”。

these 指“复数可数名词” 或多个名词（单复数均可）。

你按照这个解释，去理解就行了。