。
Trade imbalances seem to be a big problem.
Literal
Trade imbalance [subject-が] big problem [that-であるように] think.
であるように is formal: である (literary copula) + ように ('as if, seem'). 思える is the potential/spontaneous form of 思う — '[it] seems.' The whole structure renders 'seems to be a big problem' in a polished written register. 貿易不均衡 is a formal economic term.