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Today, the Fourth of July, is a day that's been celebrated in America for the past 240 years. You might be thankful for the day off from work, the awe-inspiring firework displays, or your neighbors' barbecue that you're about to attend.

Officially, though, it's the day that the Continental Congress in 1776 signed the Declaration of Independence, and began the transformation of the United States into the leader of the free world that it is today. It's a reminder of the freedoms and rights of all Americans -- those alive now, as well as those who came before us.

American companies simply aren't that "American" anymore

July Fourth isn't just a holiday celebrated by individuals and their families. Corporate America plays a big role in reminding people of the patriotism likely felt by our forefathers. From active social media accounts to products that just exude Americana -- think Jeep or Levi Strauss -- corporate America does its best to pitch in on the Fourth.

Yet the interesting reality is that, based on data from S&P Dow Jones Indices, and calculations from Marketwatch, some of America's biggest companies simply aren't that "American" anymore. By that I mean they derive the majority of their sales in overseas markets as opposed to domestically.

Based on the mid-2015 data release from S&P Dow Jones Indices, S&P 500(SNPINDEX:^GSPC) companies collectively derived 52.2% of their sales from the red, white, and blue of the U.S.A. in 2014. This means that the remaining 47.8% was generated in overseas markets.

This also marks a jump from the roughly 46% of sales that were generated in overseas markets between 2009 and 2012. Here's a rough breakdown of where S&P 500 companies are getting their overseas sales (47.8%):

• Asia: 14.3%
• Europe: 13.9%
• Africa: 7.7%
• Canada: 6.9%
• South America: 4.1%
• Mexico: 0.4%
• Australia: 0.2%

It's worth noting that the Middle East is likely being lumped in with Africa in the above figures.

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Globalization has been a key profit driver for American businesses

Globalization has played a key role in driving U.S. GDP expansion, as well as in pushing sales and profits higher for some of America's biggest companies. American companies have looked overseas for products and services in order to keep material and labor costs down. Additionally, they've turned to foreign countries to seek out faster growth potential that simply may not be present in a saturated U.S. market. Whether we like it or not, globalization has been a big reason the U.S. stock market has performed so well since the 1990s.

Obviously there are certain companies that solely operate within the scope of the United States. For example, UnitedHealth Group, the nation's largest health-benefits provider, caters solely to the U.S. market. Likewise, Verizon Communications hasn't followed primary rivalAT&T, and has, instead, chosen to remain entirely invested in wireless, broadband, and landline infrastructure within the borders of the United States.

Yet other S&P 500 giants are very reliant on foreign markets to support their business models, even if they're headquartered in the United States.

These U.S. companies are heavily reliant on foreign revenue

Among the sectors that tend be reliant on overseas markets are technology, and oil and gas.

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For example, when this report came out last year, microprocessor giant Intel, tech device behemoth Apple, and wireless connectivity kingpin Qualcomm(NASDAQ:QCOM) were generating $31.7 billion, $30.6 billion, and $22.2 billion, respectively, in revenue from Asia. As a percentage of total sales, overseas sales made up 62.3% of Apple's revenue, 82.4% of Intel's, and a whopping 98.6% of Qualcomm's.

With competition in the technology sector so fierce, it's important for tech giants to look overseas for products and labor to keep their prices competitive. Qualcomm is clearly one of the best examples of a company that's used globalization to its advantage.

Oil and gas giant ExxonMobil (NYSE:XOM) is another example of a company deriving a majority of its sales from overseas markets. Based on S&P Dow Jones Indices data, ExxonMobil nets 67.3% of its sales from overseas markets, including $115.3 billion from Canada, and another $39.8 billion from Europe.

At the end of 2015, ExxonMobil had 24.8 billion oil-equivalent barrels in proven reserves, which today is worth around $1.2 trillion. Of its proved reserves, 59% are liquids, which is up from 54% in 2014. The reason for the boost came from additions in Canada, Abu Dhabi, Angola, and Kazakhstan. ExxonMobil is a true example of what globalization can do for a company.

IMAGE SOURCE: GENERAL ELECTRIC.

Even some conglomerates generate a large portion of sales outside the United States. Healthcare conglomerateJohnson & Johnson receives 53.2% of its sales from overseas markets per S&P Dow Jones Indices, andGeneral Electric (NYSE:GE) nets 52.9% of revenue from beyond the borders of the U.S.

Even more telling with General Electric is its balance in overseas regions. The energy, transportation, and healthcare company derived $28.7 billion from Africa, $25.3 billion from Europe, and $24 billion from Asia, according to S&P Dow Jones Indices.

As you celebrate Independence Day, be reminded of the patriotism of your forefathers; but also keep in mind that, as investors, we're becoming more and more tied to the health and wealth of the global economy with each passing day.

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