perhaps the US would be mostly safe from violence, but not consequences. We're heavily dependent on international trade and any major war in another part of the world will impact us if it involves any important trading partners or their ability to trade with us.

Even in the 19th century the US was sucked into Europe's wars - the war of 1812 was essentially the American theater of the Napoleanic war - US merchants were attacked trying to trade with France/Europe, the US Navy tried to protect them saying "we're neutral let us trade" and Britain said "there's no such thing as neutral" and sent armies. Over time foreign powers got more wary of fighting the US but we still got dragged into European and Pacific wars (WWI, WWII), in large part because we kept trading with our European and Asian partners.