Less than a decade ago, U.S. automakers were struggling badly in their home market. Soaring gas prices convinced many Americans to ditch their trucks and SUVs in favor of fuel-efficient cars made by foreign automakers like Toyota Motor Corp. (TM -1.79%). This helped Toyota beat out Ford Motor Company (F -1.16%) for the No. 2 market share position in the U.S. in 2007.

Demand for trucks and SUVs is soaring again in the U.S.

The passenger car's supremacy in the U.S. was short-lived. It has been just a few months since gas prices fell back below $3 per gallon, but car sales are already withering while sales of trucks, SUVs, and crossovers are skyrocketing. Consumers prefer the extra space, power, and hauling ability of bigger vehicles -- and they're willing to pay up for those features.

As long as it lasts, this is great news for Ford and its domestic rivals, General Motors Company (GM 0.24%) and Fiat Chrysler Automobiles (FCAU). While they have definitely improved their car lineups compared to 2007, all three U.S. automakers continue to excel in building trucks, SUVs, and crossovers.

Divergent results at GM
Automakers' February sales results dramatically revealed the shift in preferences toward bigger vehicles. Let's start by looking at GM: king of the fuel-guzzling large SUV. Last month, GM's total U.S. deliveries inched up 4% year over year. But pickup sales surged 37% and large SUV sales rose an even more impressive 66%.

GM's large SUV sales have been growing at a high double-digit rate.

Meanwhile, passenger car deliveries plummeted. Combined sales of the Sonic (subcompact), Cruze (compact), Malibu (midsize), Impala (full-size), and Volt (compact plug-in hybrid) models fell from more than 60,000 units in February 2014 to fewer than 45,000 units last month.

Ideally, GM would like to be driving sales growth for both cars and trucks/SUVs/crossovers. However, GM's management and investors aren't likely to complain about the mix shift back to big vehicles -- the shift drove a $2,700 year-over-year increase for GM's average transaction price in February.

More of the same elsewhere in Detroit
The underlying demand situation is similar at FCA and Ford, although it's somewhat hidden by production disruptions caused by model changeovers.

At FCA, sales growth was also driven entirely by trucks, SUVs, and crossovers last month. The Jeep brand of SUVs and crossovers led the way with 21% sales growth, while sales of Ram pickups and vans rose 12% year over year.

Jeep sales have been driving FCA's sales growth lately.

On the other hand, car sales were roughly flat. Even that result was largely due to strong sales results from FCA's muscle cars, the Dodge Charger and Dodge Challenger. Clearly, buyers weren't turning to FCA passenger cars in search of practical cars with great fuel economy for commuting and doing errands.

Meanwhile, at Ford, deliveries of the Fiesta (subcompact), Focus (compact), C-MAX (compact hybrid), and Taurus (full-size) car models all fell double-digits year over year in February. Even the popular Fusion midsize sedan experienced a 5% drop in deliveries.

Ford's sales in the crossover/SUV category also declined last month. However, truck and van sales rose 4% year over year despite severe supply constraints for the F-150 pickup: Ford's top-selling model. Had Ford been able to meet F-150 demand, the divergence in sales between cars and trucks would have been even clearer.

What about Toyota?
As my Foolish colleague John Rosevear noted this week, Toyota still managed to sell plenty of cars last month. Including all of the company's brands -- Toyota, Lexus, and Scion -- deliveries of passenger cars rose 7.6% last month. Toyota's solid car sales can be attributed in part to having relatively fresh versions of its high-volume Corolla and Camry sedans on dealer lots.

Toyota is having more success selling passenger cars.

But even at Toyota, customer demand for bigger vehicles has been palpable. Sales of Toyota pickups, SUVs, crossovers, and minivans rose about 17% year over year. Furthermore, sales of Lexus SUVs and crossovers soared more than 46%.

This is a trend
Obviously, February is just one month. However, last month's results were just the continuation of a clear trend that has been building for several months now.

A few years ago, high gas prices seemed to have tamed Americans' appetites for trucks, SUVs, and even crossovers. But fuel prices have moderated recently, and automakers have rolled out (somewhat) more fuel-efficient versions of their larger vehicles. The result has been resurgent demand for bigger vehicles.

GM, Ford, and FCA will all benefit from this shift. Trucks and SUVs carry very high margins, and crossovers are also more profitable than mass-market sedans. The Big Three also have stronger competitive positioning in these markets than in the car market. Still, it's critical for GM, Ford, and FCA to continue investing in car designs, so they don't get caught flat-footed if the market shifts yet again.