FRANKFURT (The Street) -- Europe's allure as a tax haven for U.S. multinationals may be coming to an end.

That's because European Union regulators are closing up tax loopholes that U.S. companies have been enjoying for years. The first two to feel the heat are Starbucks (SBUX) - Get Report and Fiat Chrysler Automobiles (FCAU) - Get Report . Each will have to pay as much as $30 million in back taxes, and will face significantly higher taxes going forward.

They're not alone.

In addition to hurting its tax-haven status, Europe's crackdown may galvanize support for President Obama's efforts to address corporate offshoring of profits to avoid tax liability in the U.S.

"The actions taken by both the EU Commission and the OECD signal clearly that European countries are going to make substantive moves to clamp down on corporations shifting their profits into tax havens," said Bob McIntyre, the director of Citizens for Tax Justice, a nonprofit analysis group. "The EU's actions certainly show that the problem of offshore tax havens is one that can be dealt with. It remains to be seen whether Congress will follow the EU's blueprint for action."

Tax avoidance through the use of aggressively complicated accounting and overseas tax havens has been a steadily growing issue in the U.S. since 2008, when the Congressional Research Service found that American multinational companies collectively reported 43% of their foreign earnings in five small tax-haven countries -- Bermuda, Ireland, Luxembourg, the Netherlands and Switzerland.

Last year, the IRS released data showing that American multinationals collectively reported that 54% of their foreign "earnings" supposedly were earned in 12 well-known tax havens. An April 2015 study by the research firm Audit Analytics found that the Russell 1000 list of U.S. companies collectively reported having nearly $2.3 trillion offshore, a figure which has more than doubled since 2008.

According to CTJ, which has analyzed publicly available data from corporate public filings and published a report on their findings, "Nearly three-quarters of Fortune 500 companies operate at least one subsidiary in known tax havens," said McIntyre. "This is having a real effect on tax collection in the United States because companies now hold over $2.1 trillion offshore on which they owe an estimated $620 billion in federal taxes."

CTJ have named PepsiCo (PEP) - Get Report , Pfizer (PFE) - Get Report , Microsoft (MSFT) - Get Report , Morgan Stanley (MS) - Get Report , Apple (AAPL) - Get Report , Google (GOOG) - Get Report , Nike (NKE) - Get Report and American Express (AXP) - Get Reportas some of the top culprits. The group estimated that Apple was holding the most offshore -- $181.1 billion. Further, the group estimated the company would owe about $59.2 billion if it brought the money back to the U.S. from overseas tax havens, including those in the EU.

Seen from this perspective, the EU decision is clearly a development that marks a fairly dramatic change in the application and understanding of Continental tax law. This is also best seen in the response of both companies involved so far -- they plan to appeal. According to a Starbucks spokesperson reached by The Street, "Starbucks complies with all OECD rules, guidelines and laws and supports its tax reform process."

That said, there are few if any who expect these attempts to avoid the fines or higher liability in the future to be successful.  Further, it is also clear that there will be more impactful decisions to follow.

"The Starbucks and Fiat decisions are not material to investors," said Heather Self, a partner with Pinsent Masons, a tax law firm in the UK. "However, we await the decisions in Apple and Amazon. Apple disclosed in their 10K that the impact could be material. The decisions generally increase uncertainty and may result in higher taxes for companies with complex EU structures," she said.

This new development is also already having controversial blowback on American shores. U.S. corporations can be eligible for reimbursement by the U.S. Treasury for taxes paid to European governments. And that, according to Self, "could be a game-changer, particularly for U.S. tech giants who have previously used low-tax structures in Europe. If more EU taxes are paid, the question is whether those taxes are available for credit against U.S. taxes."

It is unlikely, however, that full deferment of such taxes, in total, will even be possible. In an environment where policy makers and President Obama are trying to repatriate these funds for U.S. tax purposes, such arguments are also not popular.

"When companies artificially shift their profits into tax havens, this can distort the companies' apparent profitability, and gives an incomplete sense of how (and where) these companies are doing business," said McIntyre. "These tax avoidance schemes have a broader cost to every American: every dollar in taxes companies avoided by Apple and other companies using tax havens must ultimately be paid for by higher taxes paid by other Americans, cuts to government programs, or increased federal debt."

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.