George Bush drew votes from conservative and moderate strongholds all across Iowa on the way to his stunning upset of Ronald Reagan in Monday's precinct caucuses, while President Carter's 2-to-1 victory over Sen. Edward M. Kennedy was convincing in all corners of the state.

Bush, who toiled quietly here for months, built a big lead in the eastern and more urban sections of the state, but also showed a broad base of support as the counting moved westward into the more rural areas.

"There was a constant Bush strength in every county in the state. That's the most impressive thing about last night," said Ralph Brown, one of Bush's top strategists in the state.

Although there are no extensive breakdowns of the voting available yet, analysts said it appeared that former Texas governor John B. Connally and Rep. Philip M. Crane of Illinois siphoned off the votes that might have given Reagan a victory here. In contrast, it appeared that Senate Minority Leader Howard H. Baker of Tennessee did not but significantly into the Bush support, analysts said.

Carter's victory in the Democratic caucuses seemed impressive in all respects. He beat Kennedy in 97 of the state's 99 counties. According to White House press secretary Jody Powell, the president beat Kennedy 3 to 2 in the cities, a presumed area of Kennedy strength, and about 3 to 1 in rural areas, where Carter's partial grain embargo was at one time expected to hurt him.

Carter won in predominantly Catholic and blue-collar areas, where Kennedy's religion and his labor endorsements should have been working for him.

With almost all of the state's 2,531 Democratic precincts reporting, Carter had 59 percent of the delegates elected to the county conventions and Kennedy had 31 percent. Ten percent of the delegates were uncommitted. California Gov. Edmund G. (Jerry) Brown Jr., who had urged his supporters to vote for uncommitted delegates, had none.

Translated into delegates to the national convention, Carter would get 29, Kennedy 15, with five uncommitted and one left to be awarded.

A computer breakdown delayed a final count among Republicans. With 78 percent of the Republican precincts reporting, Bush led with 33 percent of the vote. Reagan had 27 percent, Baker 14 percent, Connally 10 percent, Crane 7 percent, Rep. John B. Anderson of Illinois 4 percent and Sen. Bob Dole of Kansas 3 percent.

The Republicans, unlike the Democrats, simply took a straw vote of those attending the caucuses. The percentages do not necessarily relate directly to the eventual makeup of the Iowa delegation to the national convention in July.

Bush and Carter both benefited from a record turnout for the highly publicized caucuses, the first step in selecting delegates to the 1980 presidential nominating conventions. More than 100,000 Democrats showed up in homes, schools and chruch basements, compared with 38,000 in 1976. The Republicans drew an estimated 100,000 to 125,000 compared with just 22,000 four years ago.

In Charles City, 76 persons showed up for a GOP caucus that attracted only seven persons four years ago. In Cedar Rapids, a caucus at Washington High School drew 275 Republicans, up from only 40 four years ago.

GOP spokesmen claimed the turnout should be viewed as a warning sign to Democrats of a revitalized Republican Party in Iowa.

Reagan and Kennedy forces expected turnouts about half as large and clearly were caught off guard by the failure of their cnadidates to do better.

Bush relied on an elaborate campaign organization and extensive visits to the state to build up grass-roots momentum.

He did well, as expected, in most urban areas. He beat Reagan 2 to 1 in the Davenport area, 9 to 1 in the university town of Iowa City and 2 to 1 in Dubuque. He ran neck-and-neck with the former California governor in Sioux city.

But more impressive was his ability to keep down Reagan's margin in traditional conservative strongholds. In Marshalltown where Reagan held his first campaign rally in the state last August Bush held a slim lead with some precincts still out. In tiny Adams County in rural southwestern Iowa, Bush beat Reagan 695 to 100.

Reagan supporters attributed their candidate's poor showing largely to his failure to campaign more in Iowa and his refusal to appear on a televised debate with GOP opponents. "Every other candidate spent more time in Iowa than Reagan," said Irvin Hultman, one of Reagan's operatives. t"We would have liked to have seen our candidate more. It would have helped us. We would have liked to have him at the debate. That would have helped."