As mentioned most Spanish emigrants preferred culturally similar destinations with economic opportunities or places close to home. Immigration usually requires push and pull factors. What pushes the emigrant from his home country, and what pulls him to the new destination. Economically speaking, opportunities in the Americas and later Europe had much more pull for the typical Spanish emigration than the United States, Canada, Australia etc (though small numbers of Spaniards have emigrated to these three destinations).
Until the 1950s, Argentina was the preferred destination, with Uruguay and Cuba in distant second places for the Americas. Galicians were the largest number of emigrants and many of these made their way to Brazil as well due to Galician and Portuguese being almost identical languages.
Post WWII Venezuela's economic growth made it a major destination up until the 1970s. By the 1960s, Spain had impressive economic performance that made emigration less desirable. Many of these immigrants also came from the Canary Islands.
You also had large scale emigration to France and Post-WWI and Post-WWII. These emigrants were largely single male and their emigration was usually temporary, meaning few of these would have emigrated to the Americas permanently. West Germany also had a large number of Spanish guest workers until 1970 or so, but again many of these ended up returning to Spain.
Algeria was a big destination for emigrants from Murcia, Andalusia and the Balearic Islands until the early 1920s, but most of these people seemed to settle here because of the proximity to Spain (Oran's European population was overwhelmingly Spaniard).
I think for the United States to have been interesting, Argentina would have had to have had a really messed up economy. Remember that a typical Spaniard due to his linguistic ability had many more opportunities in Argentina than in the U.S.