Cause, 'Merica! Ford's 2015 F-150 in action. Image source: Ford Motor Company.

It's a well-known fact that Detroit's two largest automakers, Ford Motor Company (F -0.15%) and General Motors (GM 4.21%), depend on sales of their prized full-size trucks for huge profits. It's also well known that this rivalry has been incredibly intense and close over the years. As the rivalry continues on like a heavyweight bout, marketing and advertising will play a critical role in convincing consumers which truck is the best of the best.

Let's take a look at just how close the sales race is between the two and how GM's recent jabs at Ford's F-150 could have just received more ammunition.

What have you done for me lately?
Most of us have heard that the F-Series has been America's best-selling truck for 38 straight years and America's best-selling overall vehicle for 33 years. However, the race is much tighter when you combine both trucks under the General Motors umbrella, the Chevy Silverado and GMC Sierra. The F-Series has managed to top the combined sales of GM's two trucks each of the last five years, and the GM trucks held the advantage each of the five years prior.

In fact, if you tally sales of the F-Series from 1998-2014 it checks in with a whopping 12.6 million units sold in the U.S., which was outdone by GM's combined truck sales by roughly 46,000 units. The 46,000 sales discrepancy between the two is a figure worth less than a month's worth of F-Series sales, which is a wildly small margin of victory over that long a time span.

Because it's such a tight race between the two, marketing campaigns will continue to be critical for the trucks to edge out one another.

Cage match
General Motors posted another jab directed right at Ford's aluminum bodied 2015 F-150 recently by placing focus group members in a room with two cages -- one cage made of aluminum, and one steel. Then a huge grizzly bear clomps into the room and the focus group members race to the steel cage for protection -- a direct jab at the F-150's aluminum body.

While that advertisement has its risks for GM, which I'll point to a bit later, there could be new ammunition against the 2015 F-150.

Does American-made matter?
There are few things that embody the American spirit more than a full-size truck being used for work and pleasure. However, when you dig into the details the fact is that few vehicles are truly American-made these days. But that was one thing the F-150 truck had previously accomplished, as it topped Cars.com's most "American-made" for the previous two years.

That's no longer the case, and the 2015 F-150 has dropped off the list entirely this year -- which only ranks vehicles that are produced with 75% North American content. Chevrolet on the other hand, owns two of the top seven spots. So, is GM about to unleash some nasty un-American ads to jab at the F-150's lack of American-made parts and content? Probably not, here's why.

No room to talk
First, while GM's Chevrolet brand does own two of the top seven most American-made vehicles, the Silverado full-size truck isn't one of them. Neither is the GMC Sierra, for the record. But details like that haven't stopped GM from using slandering ads in the past. Take the recent aluminum cage and grizzly bear example. GM is taking a jab at the aluminum bodied F-150 while it has already announced plans to follow suit of Ford's aluminum bodied truck trend before 2020.

So, while GM could advertise something vague during a Silverado commercial in regards to Chevrolet owning two of the most "American-made" vehicles, the question remains: Do consumers care?

The answer is probably not, and if consumers do care it's certainly much less than in years past. That's because few cars, regardless of the automaker's nationality, are truly American-made these days. Consider that in Cars.com's 2011 model year index over 30 cars met the 75% North American content threshold. That dropped to 20 cars in the 2012 model year, and down to 14 and 10 for 2013 and 2014, respectively. This year, as you might have guessed, only seven vehicles reached that same threshold.

"You're never going to get a car made 100 percent in one country anymore," Eric Fedewa, a supply chain expert with industry consultancy HIS, told Consumer Reports. "What you'll typically see instead is larger components made near the point of sale, to save shipping costs, while small components like electric motors and actuators will be brought in from anywhere."

Ultimately, though GM's recent ads jabbing at Ford's F-150 are amusing, Detroit's automaker has very little room to talk -- if any.