A series of research studies identifies the fundamental factors behind trade imbalances (Chinn and Prasad 2003 (link is external); Gruber and Kamin 2008 (link is external); Chinn, Eichengreen, and Ito 2011 (link is external); Gagnon 2012; IMF 2012 (link is external); Gagnon 2013; Bayoumi, Gagnon, and Saborowski 2015 (link is external); and Gagnon et al. 2017 (link is external)).2 The most important factors include fiscal policy, intervention in currency markets, trend economic growth rates, per capita income levels, and prospective population aging. Barriers on financial flows have an important interaction with these factors; when financial markets are open, these factors generally have a larger effect on trade imbalances. Many studies focused on long-term factors, but business cycles may also be an important temporary factor. None of the studies found any role for trade barriers.
Figures 1 and 2 show little apparent correlation between average tariff rates or overall trade barriers and trade balances. If anything, higher tariffs are associated with lower trade balances (larger deficits). Including tariffs in regression analysis that controls for other factors yields an effect that is close to zero.
That is from Joe Gagnon, via Mark Thoma. There are some useful pictures at the link.