By John S. McClenahen The U.S. economy probably did not do as well in the just-ended second calendar quarter as it did in the first quarter of this year. Merrill Lynch & Co., New York, figures that GDP advanced only about 1% in the three months that ended on Saturday. That would equal the growth rate of 2000's final quarter and be 0.2% below the newly revised 1.2% GDP growth rate for the Jan.-March quarter of 2001. Low levels of spending on plants and equipment continue to be a drag on the U.S. economy. "Capital spending won't begin to revive until companies regain some earnings visibility. [And] that won't happen until [the fourth quarter of this year] at the soonest," says Bruce Steinberg, Merrill Lynch's chief economist.