The US Navy is the global security provider of free trade on the sea. It is one of their core functions. To ‘just go back to our own borders’ would be to completely remove the only naval force cable of providing security for free trade on the sea and thus remove huge portions of safe, navigable waters for said trade.

Who else has the navy to make it happen? China’s navy has no range, France and England’s navies have the range but aren’t large enough. Everyone else’s navy is too small and can’t deploy at range.