Trump also threatened the North American Free Trade Agreement over the weekend, while China on Monday responded to the White House's tariffs by imposing new taxes on USA imports like pork and fruits, moves that sent shockwaves through the markets.
The Nasdaq composite dropped 193.33 points, or 2.7 percent, to 6,870.12.
The S&P 500 fell 69 points, or 2.6 percent, to 2,570.
Among Oregon companies, ESI was down 8 percent, Intel was down 4.7 percent and Nike fell 4.2 percent. CBS shares were up 2.8 percent.
Amazon AMZN.O dropped more than 4 percent after President Donald Trump launched his latest attack over the pricing of the online retailer's deliveries through the USA postal system and promised unspecified changes.
After peaking at nearly $1,600 a share last month, Amazon shares have slumped recently as investors took a more cautious approach to stocks. Trump repeatedly criticized the company of late over issues including taxes and Amazon's shipping deals with the U.S. Postal Service. Technology companies including Oracle, Apple and Google parent Alphabet moved higher even though they weren't doing as well as the rest of the market.More news: Military to protect United States border
More news: An Internet Challenge Has Teenagers Snorting Condoms
More news: Google is shutting down its URL shortening service
Despite its recent losses, Amazon stock is still up about 18 percent in 2018.
Volatility was the theme in the USA equity markets during the holiday-shortened week. It wasn't the only market favorite to fall out of favor Monday.
Trump still plans to place additional tariffs on $50 billion worth of Chinese goods, with Beijing promising to respond, as reported by CNN.
Tesla (TSLA) came under regulatory scrutiny after a second crash this year involving the electric auto company's Autopilot driver-assistance system, the latest of which involved a death. Germany's DAX Index dropped 0.8 percent, the UK's FTSE 100 Index slid 0.4 percent, while France's CAC40 Index declined 0.3 percent.
Wholesale gasoline added 1 cent to $1.97 a gallon and heating oil rose 1 cent to $2 a gallon.
Health insurer Humana jumped 4.9 percent on continued reports Walmart might buy the company or announce a new partnership with it. The yield on the 10-year Treasury note stayed at 2.74 percent after a sharp decline last week.
Benchmark U.S. crude lost $1.76, or 2.7 percent, to $63.18 a barrel in NY.
The dollar edged down to 105.87 yen from Monday's 105.89 yen as currency traders shifted money into the Japanese currency, seen as a haven in times of market turmoil. Natural gas picked up 1 cent to $2.70 per 1,000 cubic feet. The euro dipped to $1.2288 from $1.2306. Hong Kong's Hang Seng bucked the trend, ending up 0.2 percent.