House-passed legislation to withdraw all U.S. investment from racially segregated South Africa and impose a near-total trade embargo faces a possible Republican filibuster in the Senate and a likely veto by President Reagan. The House adopted the disinvestment bill Thursday evening on a 244-132 vote. Supporters hailed the dramatic measure as a last-chance opportunity to bring strong economic pressure to bear to help end South Africa's apartheid system of racial separation by expanding the less sweeping sanctions adopted in 1986. But Republicans said the bill represents a ``scorched earth'' policy that amounts to declaring economic war against South Africa, a war they said would hurt the blacks it is designed to help by causing millions to lose their jobs.