The Kremlin reacted with obvious satisfaction today to a decision by the U.S. House of Representatives to kill production funds for the controversial MX missile program.

Authoritative commentaries indicated that the House vote and an unexpected decision by the Danish parliament to temporarily suspend Denmark's financial participation in the NATO plan to deploy new American medium-range nuclear weapons in Western Europe have been welcomed here as potentially the most decisive developments since President Reagan came to power nearly two years ago.

The Russians seem particularly gratified by two factors.

One is that Reagan for the first time is seen as being isolated in the American political leadership on such an important issue as the MX program. This in turn is seen as raising possibilities for additional congressional restraints on his rearmament program.

The other is that Denmark's example, as the government news agency Tass put it, "may exert an influence on the governments of Belgium and Holland, which have not yet taken a final decision on the deployment" of 572 new American missiles in Western Europe.

Diplomatic sources here said the House vote as well as the Danish decision are likely to weaken American negotiations at the Geneva talks on strategic arms and on medium-range nuclear arms in the European theater.

Tass quoted a Danish news report about "the existence of differences among NATO countries" on the issue of deployment of new U.S. arms in Western Europe. Moscow has long sought to stimulate such differences in an effort to derail the NATO deployment plan.

Tass described the House vote as a "heavy blow" to Reagan's defense policy that constituted a rejection of his "tall tales about alleged Soviet military superiority."

"If the United States really needed the MX missile to strengthen its security," a commentary issued by the news agency Novosti said, "the House of Representatives would have hardly blocked the president's plan."

Tass said the House vote "is evidence of broad discontent and concern in the country with the dangerous militaristic course" of the Reagan administration.

The commentary described Reagan as reacting with "great irritation" to the vote and said he "even likened the majority" of House members "to lunatics."

The president's statement showed, Tass said, that "he does not want to understand that by voting against the allocations for the MX intercontinental ballistic missile, the House of Representatives had actually expressed its refusal to accept the current administration's thesis about the alleged tilting of the approximate balance of strategic forces in favor of the Soviet Union in recent years."

The commentaries emphasized what is seen here as the growing importance of anti-nuclear forces in the United States and Western Europe. Tass said: "The legislators in Washington" could not ignore the outcome of the Nov. 2 referendums "in which the vast majority of Americans unambiguously" voted against the arms race.

Commenting on the Danish vote yesterday, Tass said that the legislators in Copenhagen "cannot but reckon with the powerful antiwar movement in Western Europe, and in particular in Denmark."