Europe could be dealt a serious economic blow, with hard-to-predict political consequences, as a result of U.S. Steel Corp.'s decision to file dumping complaints against seven Common Market nations.

That was the almost unanimous judgment yesterday of U.S. government officials and private trade experts assessing the potential impact of the steel corporation's decision, and the parallel withdrawal -- promised by the U.S. government -- of the steel Tirgger Price Mechanism.

The dumping suits -- which the Europeans had been trying to avert -- initially will cause the affected companies to withdraw from the U.S. market at least temporarily, rather than risk the heavy penalties to which they would be subject if found to be dumping.

"There could be a very serious confrontation between us and the Europeans," said Alan Wolff, a Washington attorney who until recently was deputy sepcial trade representative for the Carter administration.

What worries government officials here isn't European retailiation in a narrow trade sense -- under international rules there should be no legitimate countermoves to an antidumping case -- although officials are braced for some angry threats, perhaps relating to vegetable oils and synthetic fibers.

But the real fear is that at a time of economic difficulty in Europe, the loss of steel sales to the United States will bring political pressure on the seven affected governments from their steel companies and unions to respond in a broader way.

In turn, that is likely to sour official European -U.S. relationships already strained by different views over the U.S. response to Russia in Afghanistan and, in general, on Middle East policy.

Viscount Etienne Davignon, Common Market commissioner for industrial affaris, had talked to high administration officials, here last week, seeking action that might head off U.S. Steel's threatened suit. Other U.S. companies reportedly also weren't happy that U.S. Steel filed the suits, prejudicing the whole system of trigger prices.

A key question was the power level of the trigger price which, by providing a minimum import basis, was designed to give the U.S. industry some protection from imports as an alternative to major dumping suits.

The Commerce Department, which in January took over administration of trigger prices from the Treasury, was importuned by U.S Steel to raise them above the $358-a-ton level of the first quarter. The trigger price is based on the costs of the Japanese steel industry, judged to be most efficient.

When Commerce refused to raise the trigger price -- which would have allowed domestic prices to increase -- U.S. Steel made good on its threat to file the antidumping suits, claiming serous injury from European imports. In turn, Deputy Assistant Secretary John Greenwald told The Washington Post yesterday that the government would make good its own threat to abandon it once U.S. Steel had filed the suits.

Impartial experts agreed that U.S. Steel's contention that the trigger prices provided an "umbrella" for higher-cost European producers probably is true.

European producers, less efficient than Japan, almost certainly were selling steel in their own markets at a higher price than the trigger price for which they were selling it here.

But experts said that it is not conclusive that U.S. Steel would win the dumping suits, because the injury test would be based on industrywide data.

Industry observers say that most other steel producers are in better financial shape than U.S. Steel, which has been losing money on its steel operations, hobbied by some inefficient operations, while making profits on its nonsteel operations.

If the International Trade Commission should rule against U.S. Steel, the protection provided by the old trigger prices would be gone, and there is the specter, as seen by the domestic indsutry, of a major new penetration of the U.S. market by Japanese producers.

On the other hand, those White House officials who all along have felt that the TPM was just another protectionist device, would welcome such an influx as beneficial to consumers here.