Is having a U.S. brokerage account, in this case IB, not really that important if I do a long term DCA strategy?

The fees are constantly going down, so not much difference with SG based brokers now (or someday).

Hello there! It depends on how much you are dollar cost and what products you are purchasing. Fees do make a difference in the long run because of the compounding effect. It represents a high opportunity cost of forgoing higher return.