@Lundin Yes. Sometimes I buy PCBs from Sunstone (Oregon, US), BayAreaCircuits (hi-rel and decent tech levels, California, US).
Having said that, this part of the US de facto has been a prefecture of Japan since the 1970s, and a province of China since mid 1990s.
@Lundin Yes there’s a difference between a heavy¹ copper layer on a PCB and a metal core PCB². Heavy copper is created by electroplating additional copper onto copper foil. Then it’s etched, vias are drilled, etc. Metal core, on the other hand, is cut from a sheet of metal.
That technical difference should reflect in price.
¹ More than 2 oz/ft² is heavy copper, afaik.
² Single sided. I don’t know about double sided.