Based on the given information, let's analyze the options provided:

A. There are certain disadvantages for the United States economy attached to devaluation.
This can be inferred from the statement. If the dollar is devalued in terms of other currencies, it suggests that there may be certain disadvantages for the United States economy, such as potentially higher import costs and reduced purchasing power.

B. The prospect of devaluation results in a speculative outflow of funds.
This can be inferred from the statement. If there is a prospect of devaluation, it can lead to a speculative outflow of funds as individuals and investors anticipate a potential decrease in the value of the currency.

C. By encouraging exports and discouraging imports, devaluation can improve the American balance of payments.
This can be inferred from the statement. Devaluation can make American goods relatively cheaper in terms of foreign currencies, which can encourage exports and discourage imports. This shift in trade balance can potentially improve the American balance of payments.

D. The difference between the exports and imports is called the trade gap.
This is not directly stated or implied in the given information. The term "trade gap" refers to the difference between the value of a country's exports and imports, but the statement does not provide information about the trade gap.

E. It is possible that inflation neutralizes the beneficial effects of devaluation.
This can be inferred from the statement. If devaluation leads to higher prices for imported goods, it can contribute to inflation. Inflation can potentially offset the beneficial effects of devaluation by increasing domestic prices and reducing the competitiveness of American goods.

Therefore, the option that cannot be inferred from the statement is option D: The difference between the exports and imports is called the trade gap.