Import and Export are generally considered to be good things, as they allow a country to take advantage of its “comparative advantages”, the things it does more efficiently and cost effectively than others, and to reap the benefits of other countries doing the same - by removing barriers, greater efficiency for all countries is theoretically attained, and economists by and large support free trade.

Since you ask specifically about the negatives, though, there are a few. Doing a lot of imports and exports means a country is very tied in to the global market - if global demand or supply fluctuate enormously, it can be bad for a country’s economy. In the 1970s the US imported a lot of oil for example, so when the price of global oil went sky-high it caused extremely long lines at gas stations, fuel rationing, and in some case protests and riots. Today, in contrast, the US actually exports a lot of oil and petrochemicals, so when the cost of oil fell around the world, it caused a lot of problems for oil-producing states like Alaska and Oklahoma.