I think it also depends on where you are starting your company. If you are a US-based startup, you are already present in a massive market, and it may well make sense to focus on the US market only initially and only worry about selling to other countries later. Conversely, if you are based in a smaller country, then the small size of the country implies a small market which means limited domestic opportunities so the need to expand internationally early (even if just to a handful of larger markets such as the US) is much greater.
