I specifically ask about the USA because of the sheer distance involved, a quick glance at wikipedia tells me they built over 20 thousand shermans were built during World War II and it just seems unfathomable to me that it would even be possible to move that much steel across the ocean.
It was in fact an enormous logistical challenge, but the beans, bullets and billion other necessities of war did move by ship. This is one of the reasons why it was absolutely crucial for the western Allies to win the battle of the Atlantic; and, conversely, why American submarines were so useful as commerce raiders in the Pacific.