I suspect but cannot prove that a lot of the issues the US is experiencing right now exerting itself around the globe, such as lack of regional logistics ports and long supply lines and less enthusiasm from allies to join in, would apply in spades to anyone who decided to have a serious pop at the continental USA (barring globe-spanning nuclear missiles, but nobody wants to start that war right now).

Looking like a big man in your near waters, no more than a few days away from a home port, is one achievement (and it is an achievement - many nations can't do this). Sustaining a war on the other side of a serious ocean or two is a game very few countries in the world can manage right now.

The US would look extraordinarily strong to anyone bringing a war to the US.