Not necessarily, many truck usage in Europe are also cross-border traffic. There's a reason why the Netherlands, despite being rather small and transit and cycle oriented, has to make a lot of motorways.
I should have structured my post better. I mostly meant that in the time period where US truck companies could have gotten a foothold in Europe (1945-1965, approximatively) the European road network was of course destroyed, made of small, tight roads, and had few main roads to neighbouring countries. Freight mostly travelled by train or boat (up to the 70's). Plus, by 1949, half of Europe went Soviet, which didn't cut trade( as many people think), but severely limited it.
So in this context, there was little use for large trucks, and for short haul, European trucks did good enough.
Plus, of course, export taxes, gas price, etc... didn't favored US trucks, in addition to using imperial and using rare US parts instead of common European parts.
By the time Europe developped a solid highway network, European truck companies grew accordingly and took the market.