BOTH OF THE WORLD'S biggest debtors know that they have to get their national budget deficits down. But for very similar reasons of domestic politics, neither is making much progress. You have seen the great show of weight lifting by the White House and Congress here in the United States -- and the minimal results. Things are going even less well in Brazil.

Both Brazil and the United States are going to have to swing more resources into their export industries to carry their foreign debts. But the presidents of both countries resist higher taxes, and in both the people benefiting from government largess have fought spending cuts with great success.

Brazil's finance minister, Luiz Carlos Bresser Pereira, has just resigned in a dispute with President Jose Sarney. Mr. Bresser wanted to increase taxation, especially on the wealthy, and to close down a number of money-losing state enterprises. But the Brazilian congress is rewriting the constitution, and President Sarney's critics, who are increasingly numerous, want to hold his term to four years with elections next fall. Mr. Sarney is struggling to lengthen it to five years. There doesn't seem to be much more at stake than a point of personal pride, but he is pursuing it with single-minded passion and is unwilling to offend any constituency on either the right or the left.

Brazil's inflation rate is now approaching 400 percent, and it looks as though a long attack of stagflation is ahead. When Mr. Bresser took over the finance ministry last spring, the country's budget deficit was running about 6.5 percent of the gross national product. He drew up a forceful plan to get it down to 3.5 percent -- which, by coincidence, is just about the current size of the deficit here. But because of the president's adamant refusal either to tax more or to spend less, the deficit is still where it was when Mr. Bresser arrived.

The United States is obviously in a more fortunate position. There is no constitutional convention here to chill political initiative, but only the prospect of a presidential election. The inflation rate here is very low by Latin standards, although a good deal higher than last year. The country's foreign debts are enormous, and unlike Brazil's, they are still growing rapidly. But they are easier to carry, in proportion to the size of the national economy. It's the refusal to come to grips with an acknowledged danger, and the general inclination to trust to luck to rescue the country, in which the American and Brazilian performances most closely resemble each other.