That has more to do with what happened after the war: America was doing quite well and had piles of money to spend on roads and cars and suburban houses, while most of Europe was pretty devastated and had to spend everything just on rebuilding, without much left over for things like cars and highways, and so focused their investments on public transport. Even so, a huge number of European cities did end up abandoning their streetcar systems, either because the city was small enough that buses were deemed adequate or because it was big enough to have a metro system. The other big exception to the general trend was the Communist countries where public transport was encouraged over private automobiles for a range of reasons. But even in many of the ex-USSR countries, there has been a similar trend of streetcar infrastructure wearing out and getting abandoned rather than replaced.