The Panama Papers may have shed light on how globally active corporations hide their wealth from the prying eyes of revenue authorities, but their revelation did little to change major corporations' attitudes towards paying their fair share in taxes.

The steps taken by the Treasury Department this week to make it harder for companies to use "tax inversion" schemes to escape U.S. taxes have drawn a swift rebuke from several major corporations and other critics.

Inversion is an arrangement in which a smaller foreign company merges with a larger U.S. one and moves the resulting company's headquarters out of the country, thereby escaping the bulk of U.S. corporate taxation.

Typically, stock investors like inversion deals because the tax savings fatten up the bottom line of the new entity, at the expense of the U.S. Treasury and ultimately U.S. taxpayers who are left to shoulder the bulk of the tax burden left uncovered by corporate tax renegades.

Yesterday, the $150 billion international merger between Pfizer Inc. and Allergan PLC was called off because of the new anti-inversion rules.

Allergan's Chief Executive, Brent Saunders, sputtered "The rules are focused on the wrong thing: Our government should be focused on making America competitive on a global stage, not building a wall locking companies into an uncompetitive tax situation" He even went as far as calling the new rules "capricious" and "un-American."

Not to be outdone, Pfizer's CEO, Ian Read, wrote a foot-stomping op-ed article in the Wall Street Journal in which he whined that American drug companies "compete in a global marketplace at a real disadvantage" to rivals with lower tax burdens. "While the Treasury's proposal is a shot at Pfizer and Allergan, this unilateral action will hurt other companies as well."

The new rules announced last Monday by the Treasury Department involved technical changes to how past mergers are treated for the purposes of corporate ownership.

When a merged company is at least 80 percent owned by U.S. shareholders, it is taxed as a U.S. company and is subject to a 35 percent tax rate.

The new rules subtract the value of American assets acquired by a foreign company in the past 3 years, cutting the size of foreign ownership relative to that of the U.S. shareholders so that it doesn't escape the 80-percent rule.

The Treasury also limited the ability of companies to benefit tax-wise from lending money to foreign subsidiaries and earning tax deductions on the loan interest.

From now on, the Treasury will treat these "earnings-stripping" transactions as equity movements rather than loans, negating the interest deductions. Inverted companies often count on these deductions to finance their mergers.

Suffice it to say, these changes make avoiding U.S. taxes much more challenging.

The Allergan-Pfizer hookup would have put the new corporation's tax domicile in Ireland, a favorite offshore destination for U.S. corporations looking to escape paying their fair share to the IRS.

Had the deal gone through, Pfizer would have been able to tuck away an even larger share of its revenues in offshore tax havens than it has in previous years.

According to an International Business Times report, Pfizer was one of the "top 10" U.S. companies in terms of assets added to offshore stashes in 2014.

The list reads like a who's who of major corporations, including the likes of Microsoft, Apple, Google, General Electric, IBM and Gilead Sciences.

Tax inversions are a zero-sum game. Every dollar of tax that a multinational saves must be made up by remaining U.S. taxpayers. Otherwise, government budgets will be forced to shrink or the national debt will be boosted higher.

Other major corporations, including Merck & Co. and Swiss food processing giant Nestle SA, also criticized the Treasury. Coincidentally, Merck & Co. was among the top 10 offshore asset holders in a 2014 Bloomberg list of 299 companies.

The administration and Congress, although broadly agreeing that the U.S. corporate tax rate should come down, have been politically stymied from pushing any legislation forward during the current election year.

But corporate taxes aside, the real question Americans should be asking themselves is whether or not what is best for tax-reluctant multinational corporations is what is best for their pocketbooks.