What happened

It was a positive day for the markets with both the S&P 500 and Dow Jones Industrial Average ending 0.45% and 0.8% higher, respectively. Shares of TuSimple Holdings (TSP) were stuck in reverse, however. After the market closed yesterday, the autonomous driving technology company updated investors on its operations in the United States. And investors expressed their disapproval of the news during today's trading session.

Recovering slightly from their earlier decline of 22.9%, shares of TuSimple Holdings logged a 20.4% decline for the day.

So what

Inspiring little confidence that growth in the U.S. market lies on the road ahead, TuSimple Holdings announced yesterday that it's "evaluating strategic alternatives for its U.S. business." Among these alternatives, TuSimple included a sale of its U.S. business.

This news is particularly concerning for investors considering the rocky road the autonomous driving stock recently traversed in May. Last month, TuSimple seemed perilously close to being delisted from the Nasdaq, though it remains on the exchange.

While the company is pumping the brakes on its business in North America, it has achieved some recent success in Asia. Two weeks ago, TuSimple announced that it "completed China's first fully autonomous semi-truck run on open public roads without a human in the vehicle and without human intervention." Earlier in June, the company reported that it has begun testing its autonomous truck on a public roadway in Japan.

Now what

With things looking grim for the TuSimple's operations in the United States, there are valid concerns about the company's overall prospects. Prior to this news, an investment in TuSimple represented a highly speculative proposition. Now, it seems even more so. For those who have been weighing whether or not to hitch a ride with this growth stock, waiting things out to gain better clarity on its future is your best bet.