I noticed that many food items such as fruits are being grown in Chili- how does this impact the farmers growing the same foods in the United States?

It depends on the farmer.

Chile is in the Southern Hemisphere, so their seasons are opposite. Summer in North America is winter in South America.

If a local farmer is growing a crop year-round (using hothouses, etc.), well, the Chilean produce ends up being competition, just like another farmer growing the same crop year-round.

It's really up to the individual farmer to decide whether to try year-round agriculture, to switch to another seasonal crop, or to fallow their land and go fishing.

Heck, here in the United States, the government will pay farmers money not to grow anything or to grow certain crops.

Given that Chile is in the Southern Hemisphere, the fruit crop (etc.) seasons do not overlap with the same crops being grown in U.S.