The Modern Monetary Theory (MMT) idea – or at least the idea shared by some supporters of MMT online – that imports are only ever a benefit and MMT is a viable policy for all nations are badly mistaken ideas.
Now MMT would work for the US, Western Europe, Australia, Japan, South Korea or Taiwan, but not for much of the Third World.
That is, MMT-style policies are best suited for advanced capitalist nations, not necessarily for Third World countries, because most of them face severe balance of payments constraints. Increasing aggregate demand would, for many Third World nations, simply cause a balance of payments crisis, as imports surged. Moreover, a huge stream of imports from the developed world tend to cripple the development of a domestic manufacturing sector in developing world nations, just as in the 19th century our Western civilisation smashed up so much of the Third World by free trade and the de-industrialisation caused by pushing our manufacturing exports on them (Bairoch 1993: 88–89). What is needed for much of the Third World is heterodox development economics, not MMT.
And, unfortunately, MMT has its limits even in the developed world. Imports aren’t always a good thing. Domestic production matters a lot. Self-sufficiency is a good thing in many commodities, e.g., food, agricultural and primary industries. Energy independence matters a lot.
Exports matter a lot even for some developed countries, because exports bring in foreign exchange if you can’t attract foreign exchange via the capital account (that is, via people bringing in foreign exchange to buy your domestic financial and real assets).
Finally, manufacturing matters – a lot. You can’t be a really great power and maintain great wealth and an advanced modern economy without manufacturing.
The US – despite what some people think – needs to remain a manufacturing colossus to remain a great power, and to be politically independent. Self-sufficiency in many commodities and a huge manufacturing sector translates into national power. You need national power to exist in a hostile world, to make credible trade deals, and to make sure you are not the victim of aggressive, bullying policies by other national powers.
Otherwise, any large enough trading power can start a trade war and cripple you by cutting off imports.
If you think imports are only a benefit, look at the devastating de-industrialisation of large parts of the Western world, e.g., in the US, look at the hollowed-out inner cities, devastated crime-ridden communities, the de-skilled, long term unemployed workers, and the collapse of all the related industries that rely on manufacturing.
Bairoch, Paul. 1993. Economics and World History: Myths and Paradoxes. Harvester Wheatsheaf, New York and London.